“We know more about the movement of celestial bodies than we do about the soil underfoot.”
~Leonardo da Vinci

Commercial grape growers in Sonoma and Napa pay big bucks for beneficial biology consultants to come to their vineyards. And for good reason—the right blend of microbiology in their soils can significantly increase the market value of their wine by promoting more sophisticated flavors and bouquets in their grapes. When it comes to actually selling the end product, it can be the difference between producing a bottle that sells for, say, ten bucks and one that sets you back fifty or more. Just think what an understanding of beneficial biology could do for the fruit and veggies in your garden?

Organic waste decomposing at a composting facility in sacramento, California.

So what exactly is this beneficial biology? How do we ‘capture it’ and put it to work in our gardens? It turns out that the answer’s been right beneath our noses all this time. Literally! Microbes form an integral component of all living systems. In fact, if microbes didn’t exist then you wouldn’t be worrying about them, because you wouldn’t be around either! While you ponder that fact, consider one more. There are more microbial cells in and on a human (or at least one not taking antibiotics) than there are human cells in your body!

We’re going to find out how to breed microbes (it’s easy!) and deploy them in our gardens. To this end we’ve pulled in beneficial biology expert, Evan Folds from Progress Earth, to give us a practical introduction to brewing your own compost tea–and using it to grow the most delicious, chi-filled produce imaginable!

Salivating? Then you’d best read on!

Give it up for microorganisms! They perform relatively Herculean acts for their size. Microbes are responsible for aiding limitless plant processes, including helping plants feed and protecting them from disease. They even help to create the very soil that serves to support the entirety of life on Earth.  Meanwhile, many of us have become conditioned by modern marketing to foster a disdain and disrespect for microbial creatures (think hand sanitizers and antibiotics.) Healthy soil is alive with microbes. They form incredibly important mutualistic relationships with the plants we depend on for food. They break down organic matter (which is inaccessible to plants) into a form that plants can use. Think of them as little ‘compost conversion’ factories. Now start to imagine the potential for increasing the life force in your garden by learning how to breed these microbes at home! We’re talking about something called “actively aerated compost tea” or AACT for short. It’s “life juice” for your plants—a brown soup that’s full of beneficial microbiology, the essential components of any organic growing situation.

Compost Tea and Soil Food Web

Bubbling air through compost tea is essential to create a healthy, earthy-smelling brew

Brewing compost tea is easy and can be done in many different ways. You take some compost and other humus sources as a source for microorganisms and grow them to extremely high concentrations in an aerated water solution comprised of food sources and catalysts. The result? The soil food web unleashed in all its glory! Microbes and plants are natural teammates, so compost tea is simply the best way to replenish and enhance this wonderful relationship.

However, our current understanding of how to best take advantage of compost tea when growing plants can be called “rule of thumb,” at best. We know a lot about microbes, but relatively little about what they do or how to use them while growing plants.

Adding compost tea to rain water

There are potentially billions of microorganisms and thousands of feet of fungal hyphae in a mere teaspoon of quality compost. The fact is, microbes are so abundant, so pervasive in everything we do, that it’s no issue to promote astronomical numbers when discussing and marketing them in compost, or compost tea products. It’s easy to get bamboozled with all the hype surrounding compost and compost tea. Consider this: microbes are so small that up to 500,000 bacteria can fit in the period at the end of this sentence. When it comes to brewing your own microbes, high numbers are the easy part, but the number of microbes present in a biological sample is nowhere near as important as the diversity and strength of those organisms. Total numbers can be relevant when evaluating the balance of biological products or whether a humus product is stable, but it does not address the most important aspect of all—how well the product works in a real-life growing situation.

Biological Diversity and Microbe Strength

Many biological products available at your local grow store are created by microbes raised by humans in a laboratory. This biosynthetic approach is necessary for the cost effective distribution of certain microbes and has its merits, especially with mycorrhizae fungi, which cannot express their abilities without a plant and are not benefitted by brewing in compost teas. However, I believe that a biosynthetic approach cannot represent the full potential of an intact biological network. There’s no synergy amongst the different microbes as they didn’t grow up together. Remember, microbes aren’t robots, they’re unique dynamic living breathing life forms with varying abilities, even within a given species.

A key concept to grasp is that no living organism operates autonomously. In other words, there is a symbiosis, or “give and take,” found in the natural world that we humans take for granted, and therefore restrict. Think you grow your plants? Sorry but it’s far more likely that you merely get in the way and mess with the magic! All microbes operate by way of teammates. They play off of each other, with one teammate unlocking the ability of the next. The big man cannot dunk without the assistance from the point guard. When 52 different organisms (ones that were individually grown by a human in a Petri dish) are brought together as an end product intended for use in a gardening situation, the optimal result is surely compromised. Remaining with our basketball analogy for a moment longer, the team’s overall ability is hindered if all the players are not on the court and, even if they’re all present, what happens if the coach puts the players in the wrong positions?

Sure, microbes don’t play basketball (as far as we know) so you may be forgiven for thinking that it’s not feasible to identify ability in microbes. But first, check out some Bt products. Bt is a bacterium called Bacillus thuringiensis. It’s commonly used in gardening because it’s gentle with plants, but very capable of parasitizing the larval stage of common pest insects. The Bt organisms geared towards fighting larvae such as caterpillars are called the kurstaki strain and the Bt aimed at fighting mosquito larvae in water is named the israelensis strain. These organisms are of the same species and illustrate differing abilities depending on the application.

Microbes can react and adapt…by design. Did you hear about the “new” proteobacteria discovered by scientists in the wake of the recent oil spill? Look it up. BP must have been stoked!

Making and Using Actively Aerated Compost Tea

So, you want to brew your own compost tea. Where do you start? The answer is humus! Microorganisms are found dormant in quality humus sources like compost or worm castings, but can be awakened and stimulated to grow under the right conditions. There are several different methods for creating compost tea (AACT). It’s simply a matter of adding your humus source to water and using air pumps to increase the amount of air in the water solution in order to grow microbes. The final part of the jigsaw is to add some sort of food and catalysts for the microbes to grow, such as molasses, kelp, rock dust, fish, humate, sea minerals, etc.

Brewing your own AACT is similar to running an aquarium. You aerate water for fish the same way you do for microbes, or for roots in a deep-water-culture hydroponics system.

The porous bag allows microbes to escape and enter the solution while keeping the tea free from debris.

DIY Compost Tea Shopping List

You can purchase ready-to-go brewers if you want to make your life nice and easy. Alternatively you can make one yourself. To brew compost tea, you’ll need a pump, some air tubing, a gang valve, and three bubblers.

• An aquarium pump large enough to run three bubblers or air stones
• Several feet of tubing
• A gang valve
• Three bubblers
• A porous bag for the compost, like a nylon stocking OR Something to strain the final tea, like an old pillowcase or tea towel.
• A bucket

All the components of your own compost tea brewer can be obtained at your local garden store for around $60. Without sophisticated equipment it’s hard to determine technical aspects like dissolved oxygen, so it’s best to keep it simple. A small aquarium air pump is sufficient for up to 10 gallons. More air will not be harmful; it’s simply that water can only hold so much of it. If you want to use higher volumes of water, you may want to consider getting a larger air pump.

As your compost tea brews (it usually takes about 12––24 hours) you will notice a layer of foam forming on the surface. This is nothing to worry about and is actually a result of the proteins produced by biological growth. This foam is a good sign that your compost tea (or rather the microbial life within) is flourishing.

Deliberate overuse of bat guano.

Some foods sources such as bat guano create more of it, but a good fish oil (or the active ingredient in comfrey called allantoin) will keep things in motion and keep the foam down if need be. Foam is generally not a concern, especially when using suggested recipes from reputable compost tea companies.

When brewing AACT keep in mind that the higher the water temperature the greater the biological growth, but the lower the dissolved oxygen. It’s a matter of physics that the warmer the water temperature, the less oxygen can be dissolved. It is also true that the colder the water temperature the slower the biological growth. Dissolved oxygen levels above 6 parts per million (ppm) will provide sufficient biological growth, and levels around 8 ppm are attainable at room temperature. An accepted approach among compost tea enthusiasts is to brew AACT at a similar temperature to where it’s being used, for example; if your root zone temperature is 68°F (20°C), brew the AACT around this temperature.

The food source utilized when brewing compost tea can determine the microbe grown. This idea follows the concept of succession. An acre of land left fallow will begin to regenerate using annual plants (weeds), and then progress into more perennial species (grass, vegetables) until it culminates into a forest (perennial hardwoods). Over the course of this natural process, fungi become gradually more dominant than bacteria. This is not black and white, but is evident in the fungal dominance of old growth forests.

So what does this knowledge mean? Well, you can use it to brew compost teas that make more sense to what you are growing. For instance, a sugar source like molasses fed to a balanced stable compost inoculant will encourage more bacterial growth, whereas kelp or fish fed to the same inoculant will encourage more fungal growth. The same is true for other inputs, like Equisetum (horsetail), which encourages the growth of beneficial nematodes. To be clear, molasses does not discourage fungi from growing, it simply encourages bacteria more. Similarly, using a fungal dominant tea on an annual plant will not harm it in any way; it’s a better/best scenario. There is so much more to be discovered as da Vinci reminds us—we know more about the stars.

Using AACT

Microbes given a proper environment can grow to extraordinarily high concentrations. The book Secrets of the Soil states that a single microbe reaching maturity and dividing within less than half an hour can, in the course of a single day, grow into 300 million more, and in another day to more than the number of human beings that have ever lived. Further, according to the book Microcosmos, bacteria, in four days of unlimited growth, could outnumber all the protons and even all the quarks estimated to exist within the universe. This reality allows growers to use as little as five gallons on an entire acre of land, roughly equivalent to about a one cup per gallon dilution.

Compost tea can be used in unlimited ways and really cannot be used incorrectly unless you are overwatering your plants. Some growers choose to use compost tea on every watering, but weekly applications or on reservoir changes would be sufficient. It is even possible to experience benefits from compost tea with just one application. After all, you’re dealing with living organisms that can populate and reproduce by themselves if given proper conditions.

It is a common supposition that synthetic products (i.e. mineral based nutrients) kill microbes. While this is certainly true on some level, using compost tea with synthetic nutrient regiments can produce good results. The image inset illustrates the use of a leading compost tea brew used at one cup per gallon on weekly reservoir changes in a mineral-based hydroponic situation growing jalapenos.

Again, it’s a better/best scenario; you’re better off using compost tea and mitigating the potential harshness of your mineral-based nutrients than worrying about the microbes dying.

It is always advisable to check nutrient concentrations with a meter before using a tea on sensitive or special plants, but by keeping inputs at or near recommended amounts there should be no fear of burning. “Burning” a plant is actually a water stress based on total ion concentration. Having too many ions around a root system sucks water out of the plant via osmosis, causing the plant to respond by sending its available water into the middle of the leaf and leaving the edge to burn. Because compost tea is created at relatively low concentrations (600-800 ppm) burning is a non-issue when used at recommended levels.

As if to underline the previous point, compost tea can be used with seedlings and cuttings with great success. The sooner and more microbes used the better, even in hydroponics. Use a gallon of compost tea to 20-50 gallons of water in hydro reservoirs; some growers even use compost tea concentrate as their primary reservoir solutions. Consider using organic and organic-based nutrients as food sources for biological inoculants. It is not necessary to feed microbes after you have implemented them into a garden, but it can certainly have a positive influence. After all, natural farming is about feeding microbes, not the plant.

Compost Tea as a Foliar Application

You can even use compost tea as a foliar spray. Some growers spray their plants every day, but once a week will do the trick for measureable results. When using compost tea you are harnessing a synergy of living microbes for general benefit, however, this is one of the occasions when a targeted biological product can be effective. Many times the microbes used in human designed microbial products are found naturally in compost, but not in high enough concentrations to make them applicable once pests or disease have struck. In the end, a pest or disease is simply a biological imbalance of some sort, so when one trophic level gets out of whack a higher concentration of a certain microbe can work effectively.

The active ingredient in many biological fungicides is the bacterium Bacillus subtilis, which is found naturally in compost. This concentrated organism will work better on a disease outbreak, but if used consistently, compost tea can work preventatively to allow the disease to express itself in the first place. The more consistent you are in delivering microbes to the leaves and root zone of your plants, the more benefits you will receive.

Compost tea can even help control pests if used consistently, many bacteria found in compost seek protein, which is what comprises the exoskeleton of many target pest species. As with any new endeavor in the garden, isolate a test plot and experiment before implementing it into the entire growing situation.

There is no real precedent for using Actively Aerated Microbial Extracts (AAME) in compost tea brews, but it’s certainly a good idea for experimentation. Some grow stores set up multiple compost tea units for grow/bloom or bacterial/fungal purposes. I anticipate that we will start seeing them for pest and disease control too in the near future.

AACT Brewers

There are varied compost tea units available on the market, everything from a five gallon bucket to large commercial units. For the most part, the unit you choose will be based on volume size and convenience, not biological performance.

There is a healthy debate regarding the importance of the size of the air bubble produced by air diffusers and another on whether they need to be used at all. While it is certainly true that the smaller the bubble the more surface area exposed to the solution, it is unclear whether this really makes a difference based on maximum dissolved oxygen levels considering water holds a finite amount of oxygen relative to its temperature.

Filter bags to hold compost are also a point of difference between respective models. They are used strictly for convenience so that the compost tea brew does not clog up sprayers after creation. This can save time, but must be balanced with what is not extracted from the physical compost when brewing. As mentioned above, microbes hold on really tight. A quality humus is colloidal and most inputs used are soluble, so a filter bag is not absolutely necessary. You can always filter it after you are done brewing.

It is vital to use quality water when brewing compost tea, and in your garden in general. If you are unsure of your water source, use a filter. There are quality reverse osmosis (RO) filters and de-chlorinators on the market for reasonable prices. Most nutrient solutions are not designed to account for what comes through the tap, so if possible start from zero ppm. Remember, chlorine kills microbes and it’s added to just about every public water supply in some form for this very reason. Bubbling your water will remove chlorine in a couple of hours, but not chloramines, its more persistent cousins—also used in many municipal water supplies. At the very least, let your water sit out for 24 hours before using it to brew tea. Ideally, invest in a reverse osmosis water purification system.

Composts, Inoculants and Food Sources for Compost Tea

When brewing compost tea, starting with a quality microbial product is essential. This is a major problem with people who compost in their back yards. Organic matter doesn’t melt; it’s biologically digested. It’s not advisable to use manure to make compost tea because manure is not yet plant food. This is why black cow “compost” at the hardware store costs $1 a bag. It’s aged manure. It’s mulch, not plant food. Remember, trees in a forest don’t eat leaves; they eat what the microbes make of them.

Some growers use worm casings as the sole basis for their compost teas. While this is certainly a viable option to brew tea, worms are predominately a bacterial organism, and do not contain some of the trophic levels of beneficial organisms, such as fungi, nematodes, protozoa, ciliates, etc. that provide vital benefits to plants and gardens. Worms sequester bacteria in their gut in order to work their magic, like termites use fungi to digest the wood they eat. To brew a better tea, consider using worm castings along with a balanced humus product.

Food sources for compost tea include molasses, kelp, fish, bat guano, and generally anything that was once alive that is soluble enough to be put into solution, even fruit pulp. It is important to note that recipes and preferences vary widely, for instance, some may recommend up to 16 tablespoons of molasses per 5 gallons of water, others only 1 tablespoon. Be sure to experiment based on these general recommendations, but here are a couple of simple recipes:

Use the formulating company’s recommendations for humus and catalyst per gallon, then for a bacterial dominant tea, use 4-6 tablespoons of molasses and 2-4 tablespoons of kelp to five gallons of aerated water. Reverse the ratio for a more fungal dominant tea.

Three Simple AACT Recipes (All for 5 Gallon (19L) brewers)

Bacterial Dominant Tea

1.5 pounds (700g) bacterial compost or vermicompost
3-4 tablespoons (45-60ml) liquid black strap molasses
4 teaspoons (23g) dry soluble kelp or 2 tablespoons of liquid kelp
3-4 teaspoons (15-20ml) fish emulsion

Equal Ratio – Fungi : Bacteria Tea

1.5 pounds (700g) 1:1 fungi to bacteria compost
3-4 tablespoons (45-60ml) humic acids
4 teaspoons (23g) dry soluble kelp or 2 tablespoons of liquid kelp
3-4 teaspoons (15-20ml) fish hydrolysate

Fungal Dominant Tea

2 pounds (900g) fungal compost
3-4 tablespoons (50ml) humic acids
2 teaspoons (10ml) yucca extract
4 teaspoons (23g) dry soluble kelp or 2 tablespoons of liquid kelp
4-5 teaspoons (20-25ml) fish hydrolysate

Recipes from ‘The Compost Tea Brewing Manual’, 5th Edition by Dr Elaine Ingham.

Fish-based natural fertilizers are generally obtained in one of two forms, condensed fish solubles known as emulsions, or enzymatic digested fish known as hydrolysates. Fish hydrolysate is cold processed (minced, enzymatically digested and liquefied) to preserve proteins for quick turnover by microbes into nutrients for plants. Emulsions are created using extreme heat, and while they may be easier to work with because they are further refined, the processing removes valuable ingredients and denaturing nutrients. While both fertilizer forms can benefit a compost tea, hydrolysates retain the natural oils from the fish that are a very potent fungal food.

Mineral Catalysts

One thing that is not discussed enough in the compost tea community is the use of mineral catalysts. Catalysts, as we know, change the speed of a reaction. It’s important to understand that microbes work indirectly via chemical decomposition. In other words, bacteria don’t chew on a banana peel in a compost pile, they offer up an enzyme (biological catalyst) that works to chemically break it down. Enzymes are specialty proteins that work like keys to a lock for important biochemical reactions within living organisms, plants and people included. All enzymes incorporate a single molecule of a trace mineral—such as manganese, copper, iron or zinc—without which an enzyme cannot function. We all know the benefits of adding enzymes to our gardening systems, but not many growers know that you get free enzymes from microbes.

Microbes help plants eat and, in return, plants feed microbes. In fact, over half of the energy derived through photosynthesis by plants is fed to the soil as exudates. Think of an exudate as a meal for microbes. Plants actually know what they need, they just can’t tell us. This means that plants have the ability to attract specific trophic levels (imagine the balance of the big fish and the little fish in the ocean) of microbes by preparing food from its surrounding environment that attracts those capable of generating what is deficient in the plant. This biological/plant network, or intelligence, if you will, cannot be established overnight, but it can be tapped into if we are aware of it. This is especially true when growing indoors in artificial environments.

It’s important to provide everything for plants so they can be allowed to eat what they desire, but it’s even more important to allow microbes a complete tool kit. Not doing so is like hiring someone to build a house and only providing them half the tools. The pictures inset illustrates a side-by-side conducted with a broad-spectrum mineral product. The tea sample on the left was brewed in the presence of many more elements than the tea sample on the right. Note the enhanced foaming and darker color after only four hours.

Other catalysts to consider are rock dusts, yucca extract, or any broad-spectrum natural mineral. Remember, these materials are not “food” for microbes; they help microbes eat their food.

Buying AACT

Your grow store might be one of the many who offer up their own in-store brew from units operated inside the store. If you choose to purchase compost tea from a gardening store, be sure to use it as soon as possible. We have seen evidence of beneficial life for up to three days under a microscope with some systems, but it is always advisable to use it the day you get it from the shop. Make sure to ask your retailer about the components of the compost tea being brewed, including the biological source and whether mineral catalysts are being used. If they have a microscope set up, even better. Make a habit of reconciling the microbes you see under the scope before you take it home with the results you are getting in your garden.

Some models found in stores involve refrigerating brews and coordinating pickups on certain days, while others encourage running the units perpetually by adding food source, catalysts, and microbes daily based on the amount of water added to the unit.

Brew Times

The most commonly heard figure for brew times is 12-24 hours. If pressed for why, a common answer is because bacteria are most active in these stages. While bacteria are beneficial to plants, so are many other microorganisms. Take protozoa for example. It is well known that compost tea brewed for over 24 hours begins to develop protozoa and ciliate dominance. (The brew “matures.”) Protozoa are extremely efficient nitrogen (N) cyclers, so why would a grower looking for more nitrogen not brew their tea longer to populate more protozoa dominance? Further, they are also the shredders in the soil; they eat bacteria and fungi like a shark eats fish in the ocean. Humus is actually the guts of microbes. They have digested available organic matter to create stable dormant humus (plant food). The guts of microbes are actually fertilizer bags. Why wouldn’t we want protozoa in there creating nature’s plant food shredding up bacteria?

There is no “right” way to brew compost tea, only better and best. Before long we will have developed biological feeding schedules that direct growers on how long to brew their compost teas given humus, foods, and catalysts to accomplish the microbe spectrum that makes sense for the plant and stage of growth, like we do mineral products. If one wants bacteria to use as a foliar, use molasses and brew for 12 hours. For a higher fungal: bacteria ratio for hardwoods, brew 24 hours using fish hydrolosate and humates. Feed hay has shown promise in increasing protozoa counts, so brewers can use it and brew for 48 hours to sequester more for their gardens. The possibilities are endless.

Some growers are experimenting with aerating their microbes for a period of time before adding food sources. The idea is that some microbes wake up faster than others, so brewing without food lets all of them get their feet on the ground, so to speak. Makes sense, but much more research needs to be conducted. The new frontier in natural gardening will develop around these ideas. One thing is for sure, we’ve got a lot of work to do. But, hey, it could be worse, we could be sitting in a cubicle.

If we approach the biological situation of our soils and hydro systems humbly, we will be in a far greater position to benefit. We can get more out of our plants than we have come to expect. Growing plants is about much more than feeding a plant directly, it’s about taking stock of their total environment, including the biological (microbial) and energetic (biodynamic) aspects of the growing situation. Rather than listen to ourselves, let’s listen to our plants for a change.

If you’ve never used compost tea with your plants, you’re not maximizing the genetic potential of your garden. Consider this your clarion call. Stop by your local garden store and get started today.

“Nutrition as it is today does not supply the strength necessary for manifesting the spirit in physical life. A bridge can no longer be built from thinking to will and action. Food plants no longer contain the forces people need for this. So long as one feeds on food from unhealthy soil, the spirit will lack the stamina to free itself from the prison of the body.”   —  Rudolf Steiner • Creator of Biodynamics (1861-1925)

WORDS: Evan Folds

In the last issue we talked about just what aquaponics is (the marriage of aquaculture and hydroponics) and how it works. I described system types and then went into some detail about the creatures that live in a media-based aquaponics system: fish, plants, bacteria, and worms.

This article is the second installment in the two part series. We will now focus on what you need to know in order to build a media-based aquaponics system, including considerations about the fish tank, the grow bed, the plumbing, and the media.  So let’s dive right in.

Fish tank

The size of your fish tank will define the ultimate size and flexibility of your aquaponics system, so consider the tank size early in your design process. If you are building a small, desktop system using an aquarium, you will be restricted to aquarium fish that will live comfortably in the size aquarium you own. If you want to grow larger, edible fish, the most important rule-of-thumb when choosing a tank is to make sure it is made of sturdy, food-grade or food-safe materials. Next, make sure that the tank is at least 18” deep (457mm), and holds at least 50 gallons (189 Liters) of water. Tanks need to hold approximately 50 gallons (189 Liters) or more in order to grow “plate sized” fish (12” and 1 ½ lbs, 300mm and 680g).

Aquaponics fish tanks can be made from just about any structure that has satisfactory dimensions. They needn’t even hold water – just line them with EPDM pond liner. You can also use everything from recycled bathtubs, stock tanks, and IBC tanks, to recycled barrels.

Since you will find it difficult to move your fish tank once you fill it with water, you should carefully consider where you place it. Ideally the fish tank should be located indoors or outdoors in the shade. Fish don’t require sunlight to thrive and the extra heat and algae growth from sunlight can become a problem. Also, be sure the tank is on a solid surface that can handle the weight of the tank when filled with water. At 8.3 pounds per gallon, you will quickly reach a weight that might exceed the structural limits of the surface you are planning to use.

Wherever you choose to set up your tank, you will be well served to at least partially cover it to help prevent debris, children, and pets from falling in. Covering it will also lower the amount of light reaching the tank. This will help you keep control of the tank’s temperature and reduce algae.

Grow bed

Fish tank volume governs the maximize size of your grow bed. Here is why. The plants need the fish waste to thrive. The bigger the grow bed and thus the more plants, the more fish waste required. Simple – you need enough fish to support your plants. In general the recommended grow bed to fish tank ratio is approximately 1:1, i.e. the fish tank volume should be approximately equal to the volume of the grow bed. This ratio can also be thought of in gallons per cubic foot, striving for 6 gallons (22 liters) of fish tank to every cubic foot of grow bed. For example, a 50 gallon (189 liter) tank would be able to support 6 to 8 cubic feet of grow bed. You can extend this rule of thumb all the way to 2:1 (twice the fish tank volume to grow bed volume) but be sure to reduce the stocking density of your fish tank accordingly as this approach reduces your ability to filter the fish tank water with the grow bed plants.

Aquaponics grow beds should be about 12” deep (300 mm). 12” provides enough depth to support most plants and encourages the bacteria and composting red worms in the grow bed to fully establish themselves. A 12” deep bed never needs to be cleaned out because the robust eco-system enabled by a 12” deep grow bed takes care of this for you. Below is an excellent explanation by Australian Murray Hallam of grow bed dynamics – reprinted with permission from his new Aquaponics Secrets video:

Surface or dry zone (Zone 1) - The first 2” (50mm) is the light penetration and dry zone. Evaporation from the bed is minimized by the existence of a dry zone. This dry zone also protects the plant base against collar rot. Additionally, by ensuring that this zone is kept dry, algae is prevented from forming on the surface of the grow bed and moisture related plant diseases such as powdery mildew are minimized.

Root zone (Zone 2) - Most root growth and plant activity will occur in the next zone of approximately 6” – 8” (150 – 200mm). In this zone, during the drain part of the flood and drain cycle, the water drains away completely, allowing for excellent and very efficient delivery of oxygen rich air to the roots, beneficial bacteria, soil microbes, and the resident earth/composting worms.

During the flood part of the cycle, the incoming water distributes moisture, nutrients and incoming solid fish waste particles throughout the growing zone. The worm population does most of its very important work in this zone, breaking down and reducing solid matter and thereby releasing nutrients and minerals to the system. “Worm Tea”, as it is commonly known, will be evenly mixed and distributed during each flood and drain cycle. “Worm Tea” and the fish are entirely compatible.

Solid collection and Mineralization Zone (Zone 3) - This is the bottom 2” (50 mm) of the grow bed. In this zone fish waste solids and worm castings are finally collected.  The solid material has been reduced by up to 60% by volume, by the action of the resident composting worms, and microbial action. During each flood and drain cycle, what is left of the solids percolates down into this zone further and final mineralization occurs in this area via bacterial and worm activity. Due to the excellent action of the flood and drain cycle, this bottom area is kept “fresh” and vital by the excellent delivery of oxygen rich water during the flood cycle.

Warning: Do not use metal containers, not even galvanized metal, for either the grow bed or the fish tank. Metals can quickly corrode, throwing your system off-balance by lowering your tank’s pH. Metal containers may also leach undesirable chemicals into your system. Copper and zinc are particularly dangerous to fish. As with the fish tank, make sure the grow bed you choose is made of sturdy, food-grade or food-safe materials.

Media

The growing media should be inert, meaning that it should not be biologically active or decompose. This enables the best bio-filter for your fish waste and the cleanest system overall. Most aquaponic gardeners use either gravel or expanded clay pellets (e.g. Hydroton).

If you use gravel, it should be ¾” (20mm) to 1” (25mm) in diameter in order to optimize the air exchange within the media for the roots of your plants. Caution: be certain you know where the gravel is from. Many types of gravel, especially granite, can leach lime and other elements, which will adversely affect your pH levels and potentially kill your fish, plants, and bacteria. Marble also tends to increase pH to levels that can quickly be fatal to bacteria, and eventually the fish and plants.

Expanded clay pebbles are more expensive than gravel, but are 50% lighter and more porous so they have optimal gas and water exchanging properties. Best of all, because of their round shape, it’s easy on your hands, roots and stems of your plants – making planting and maintaining your system a pleasure. Plus, you will have no worries as to where it came from! We think it is worth the investment because you will have it for the life of your aquaponic system.

The top 1 – 2” of your grow bed should be left dry to help prevent fungus, gnats, algae problems, and moisture related diseases (see the Dry Zone above).

Plumbing

Flooding the grow bed delivers nutrients to the plants and the bacteria; draining the bed oxygenates the water, the plants roots, and the bacteria. Systems using this method are called flood-and-drain or ebb-and-flow systems, and are what most media-based aquaponic systems employ.

There are three standard flood-and-drain style plumbing systems used in media-based aquaponics: timer based, bell siphons, and flush valve systems.

Timer based systems are the most common and the easiest to install. They are comprised of four components: the water-in pipe, the over-flow drain, a timer, and the pump. To set up a timer-based system you simply attach a pump to a timer and set it to power the pump for 15 minutes every 30 – 45 minutes. While this is much more frequent pump activation than in a traditional hydroponics system it is necessary to provide sufficient oxygen to the fish tank, sufficient filtration for the fish, and sufficient oxygen in the grow bed for all the biological activity (as the water drains from the bed it pulls oxygen behind it through the bed).   Since pythium (root rot) is almost non-existent in aquaponics there is no increased danger of disease because of this increased irrigation frequency. Next place the pump in the fish tank and attach the pump to the water-in pipe that goes into the base of the grow bed. When the pump is activated, water will move from the fish tank into the grow bed until it reaches the level of the overflow drain. The overflow drain should be set to drain at 11” so that the top one inch of the grow bed will be left dry. After 15 minutes of flooding the grow bed, the timer will turn the pump off, allowing water to drain back through the water-in pipe and out through the pump. Though this system is common and easy to install, the downside is that turning the pump on and off can shorten the life of the pump.

In the bell siphon (AKA auto siphon) system the water pump constantly pumps water from the fish tank into the grow bed. As the water rises, it fills the interior of the bell siphon positioned within the grow bed. When the water reaches the right height, it spills over a pipe within the siphon and creates a low pressure area within the siphon that triggers the siphoning action. The siphon rapidly draws the water from the grow bed into the fish tank until the grow bed is nearly drained, at which point air enters the siphon, the low pressure within the siphon is lost, and the siphoning action stops. Since the pump is always on, the grow bed begins to fill once again and the cycle repeats. This may seem confusing at first, but the bell siphon system can be a great option to explore, as leaving the pump on at all times will increase the longevity of the pump. Plus the extra heat that the pump may generate is actually a benefit to aquaponic systems growing fish that prefer warmer water.  Again, because pythium is so rare in aquaponics the extra heat does not pose an increased risk of disease. There are many excellent videos about the construction of bell siphons available on the internet.

Flush valve systems work very much like a flush toilet. This system requires that a flood tank be added to your fish tank and grow bed setup. The flood tank, being similar to the tank of a toilet, is placed above the grow bed. The grow bed, being similar to a toilet bowl, is placed below the flood tank with the fish tank being the drainage point. Water is constantly pumped from the fish tank into the flood tank. A small siphon collects water that fills a container, which acts as a weight. Once the water is heavy enough it triggers a standard toilet flush valve. This then allows water from the flood tank to drain into the grow beds and then into the fish tanks. The water-filled weight has a hole in it that makes it drain slower than it is being filled, so once the flood tank has emptied the small weight begins to drain. Once the small weight has drained it again is light enough to close the standard toilet valve, re-initiating the cycle.

The pump is the heart of an aquaponics system. When you select a pump, consider a simple rule of thumb – choose one that can, at a minimum, cycle the entire volume of your tank in an hour. If, for example, you have a 100 gallon (375 Liter) tank, than you will want a pump that can pump at least 100 gallons to the height of the grow bed every hour.

It is important to have backup aeration for your aquaponic systems. If your pump fails, your plants will be fine for a day or two but a few hours without moving water could lead to dead fish due to oxygen deprivation.

Starting up your system

So now you just put in the fish and the plants, plug in the pump and start growing, right? Not so fast! First you need to establish nitrifying bacteria in your aquaponics system, a process called “cycling”. Without these bacteria, the ammonia the fish produce will not be converted into nitrates, causing the fish to die from ammonia poisoning and the plants to starve from lack of fertilizer.

The key to cycling is patience. To initiate cycling, ammonia must be introduced to attract the naturally occurring nitrosomonas bacteria. After another two weeks, or so, the existence of nitrites will attract nitrobacter bacteria. This second type of bacteria is what will change the nitrites into nitrates. Nitrates are nearly harmless to the fish and are consumed by plants as food, therein filtering the water. After approximately 30 days of cycling, you will reach your goal – low ammonia levels. Now you can fully stock your tank and plant your grow bed. For even faster ways to cycle your system, read on..

The Nitrogen Cycle

There are many ways to introduce ammonia to initiate the cycling process in a fish tank. These are generally broken down into two categories: with fish and fishless cycling. Most people use live fish to introduce the first ammonia to the tank and start the nitrifying process. Since ammonia is poisonous, and there will be no bacteria to convert the ammonia for a few weeks, assume these introductory fish are “sacrificial” and may not survive.

If you choose this route, avoid pet store “feeder fish” since, generally speaking, they tend to already be diseased or near death due to poor conditions. Black skirt tetras, goldfish, zebra danios and barbs are good choices to start cycling your tank. Only feed these first fish once a day during the cycling process.

If you prefer cycling without fish, you can initiate the cycling process by introducing small amounts of pure ammonia (clear ammonia, 100% ammonia or pure ammonia hydroxide), vermicompost, or “humonia” (also known as “pee-ponics” where one urinates into the system to introduce the ammonia).

You can speed up the process by actually introducing the nitrifying bacteria yourself with river or pond water, filters or gravel from an already established tank, or with commercial nitrifying products.

Whether using fish or fishless cycling, it is important to use a test kit to monitor the system daily so that you always know what part of the ammonia cycle the system is in. Be sure to keep the pH between 6 and 8 (at 8 or above the cycling process stops and the ammonia becomes highly toxic) and the water temperature above 50°F/10°C (80°F/27°C is optimal).

Once your ammonia and nitrite levels drop and nitrates begin to appear, it is safe to add plants and fish to your system. If you stick with the recommended fish stocking density (no more than 1 pound per 5 gallons of water), keep your beds fully planted, and follow all the other recommendations in this article, you will find that your grow bed grows better and better with time. Happy gardening!

WORDS: Sylvia Bernstein

Life is a miracle and cultivating plants is part of that miracle. In caring for our plants we form a symbiotic relationship with them. We watch our plants grow and do everything we can to help them reach their full potential. When we harvest and consume our crops, those same plants we cared for help us to grow! Seasoned gardeners are aware that this is just one relationship, one link in the miraculous chain of life. It’s so marvelous that many beginner gardeners focus exclusively on that ‘link’ – maybe because it’s the one that happens to be most directly appreciable to our senses. But there is a whole universe right beneath our noses that exists just beyond our powers of vision. It is a hidden world of microbiology that exists in the soil itself. We tend to appreciate this indirectly through effects, rather than causes, observing a plant as “healthy” or “diseased.” But with a little knowledge, seasoned with some imagination (or a powerful microscope!) the true extent to which we share this world can be revealed and the way in which we care for our plants is transformed.

A World In A Teaspoon

Okay, enough romantic talk of Mother Nature. Let’s move on to some mind-blowing facts. And these facts really are mind-blowing! Don’t just “uhuh” as you read these. See if you can actually visualize what is about to be described:

Imagine taking a teaspoon and dipping it into some living soil. Lift it up and hold it in front of you. What do you see? A teaspoon of dirt?

A teaspoon of living soil contains 100 million to 1 billion bacteria, 1 to 40 miles of fungal hyphae, and 1,000-100,000 protozoa!

40 miles of fungal hyphae in one teaspoon!? Now do you see we’re talking about another world within our world? What are these organisms? Well, they are all part of this whole chain of life that helps to grow your plants. These organisms are as real as they are small. And in their huge numbers, they play a really important role in plant health and growth. The bacteria eat the exudates (simple sugars, carbons, carbohydrates) that the plant puts out through its roots, which are then eaten by the protozoa. What is excreted by the protozoa is now plant-available nutrients. Beneficial fungi protect the plant from pathogens and harmful microbes, as well as creating pathways in the soil that bring water and nutrients back to the plant from larger distances. Bacteria and fungi work together in decomposing organic material and making the nutrients plant-available. This is a sustainable process known as “nutrient cycling” that allows for the growth of healthy plants, without the need for fertilizers, pesticides, and other chemicals. After all, there’s no one out there putting Miracle-Gro on our rainforests each year, yet look at how successful plants are at growing in these microbial-rich environments!

The War on Terra

Most soil these days lacks the biology necessary to cycle nutrients to the plant and protect it. Where did they go? They were killed off by so-called modern agricultural methods or “the war on terra” – years of abuse including overuse of synthetic fertilizers, pesticides, fungicides, over-tilling, and compaction.

Chemical fertilizers and other -cides contain salts. Remember back to high school science where you learned about the process of osmosis? It’s the movement of water through a cell membrane from a solution of low solute concentration to a solution with high solute concentration. In living soil, water is locked up in the cells of the microorganisms. With the proper biology in place, you can cut back on your watering by up to 30%! When salts in the form of chemical inputs are added to the soil, the water is drawn out of the microbes and they are either killed or go into a dormant state. Now the plant is dependent on you to provide all of its food and protection. That’s why you have to fertilize on a regular basis.

In addition to damaging the biology in the soils, these chemicals are having other impacts of much greater consequence. Nitrates from fertilizers are leaching into our water system, and pesticide exposure has been linked to a variety of serious diseases such as cancer. There’s a reason that lawn companies recommend keeping children and pets off lawns after they’ve been sprayed. These chemicals are highly toxic!

So what’s the alternative? There is a shift from our current N-P-K paradigm towards an organic way of gardening by feeding the microbes in the soil and letting them do the work for us. Our ancient ancestors gardened in this manner long before we knew what bacteria were! Fertilizer was in the form of manures, which were decomposed by the microbes and provided all the nutrients the plant needed.

Creating Life in Soil Again: Compost Tea

Using present day technology, we are now able to add these beneficial organisms back into our soils and feed them through a variety of organic inputs. The three best things you can do for your soil is to top dress with compost, mulches, and compost tea. Since many of you probably already know about the benefits of compost and mulch, I’d like to focus a bit more on compost tea.

When I say compost tea, I’m referring to actively aerated compost tea, or AACT for short. This distinction is important because there is a big difference between throwing some compost or manure in a bucket and letting it sit for a couple of weeks, and AACT.

AACT is an aerobic water solution that has extracted the microbe population from compost along with its nutrients. The concept behind compost tea is quite simple, though the actual process becomes scientific and has many variables that need to be accounted for. The idea is that compost (full of beneficial microorganisms) is put into water and then nutrients or foods for the microorganisms are added to allow the bacteria and protozoa to multiply rapidly and the fungi to grow. Air is sent through the water to keep the dissolved oxygen levels above 6 mg/liter, as this selects for the aerobic microorganisms, which are the ones found to be most beneficial. At the end of the brewing cycle, what you have is a concentrated liquid literally teeming with billions of microorganisms that can be sprayed directly onto the leaf surface of your plants or onto your soil. This puts the “good” biology where the plant needs it to protect itself. It keeps the plant healthier and helps to fight off potential diseases. The “good” biology occupies the infection sites on the leaf surface and survives by consuming the exudates that the plant puts out. The “good” biology then out-competes the pathogens for the space on the leaf surface or around the roots (rhizosphere). This is how plants protect themselves and thrive in nature.

It is possible to make bad AACT. If you don’t start with good compost, don’t add the proper amount of nutrients, or keep the brew sufficiently aerated, you could be selecting for pathogens rather than beneficial microbes and end up with a tea that will have little to no effect on your plant or possibly even do damage.

Along with compost tea it’s important to do applications of other bio-amendments such as soluble seaweed, humic acids, and fish hydrolysate, for example. Seaweed serves as a bacterial food substrate and also provides additional benefits for your plants in the form of growth hormones, increased stress resistance, and faster plant response. Humic acids serve as a fungal food, and also chelate (bond with) minerals in your soil and make them available (many minerals in your soils are “locked up” or unavailable). These sorts of applications work by feeding the microbes, which in turn feed your plants.

When gardening in this manner, it’s important to adjust your application rates or program to fit within the needs of your garden. I’d suggest an initial topdressing of your garden with compost and an application of compost tea, adding soluble seaweed and humic acids to the tea after brewing. Then, another application 2-3 weeks before planting and another one when you plant your starters (adding mycorrhizal fungi into the hole at this time). In the fall, I’d add a mulch to your garden, followed by an application of compost tea (to speed up decomposition over the winter). You may or may not need an organic fertilizer (NPK below 10-10-10) to supplement the rest of your program.

Once an organic program has been established, typical application rates of AACT, humic acids, and seaweed are only 3-5 times per year. Now the plant is in charge, and the organisms are in place to cycle the nutrients for the plant. This is what sustainable gardening is all about!

WORDS: Tad Hussey, Keep It Simple, Inc. www.simplici-tea.com

All sounds rather slick, right? After all, the key to huge harvests is providing a whole spectrum of optimum conditions for your plants – like a series of links in a chain. However, there’s one thing missing from this garden – an essential building block of the sort of harvests your plants want to give you. MICROBES.

Beneficial Microbes

Microbes may be small, but they’re taking off in a big way as indoor gardeners discover new ways to harness the benefits they bring. And leading the pack is John Perrino of Vermicrop Organics, California.  He’s taken some time out from his crazy microbial world to explain what microbes are, what they do, and how we urban gardeners can use them to take our gardens to the next level.

Perhaps I shouldn’t attempt to summarize everything in the first sentence, but here goes: Beneficial microbes increase the efficiency of your nutrients. Put another way, microbes allow your plants to feed more. Even the highest quality nutrients can be made more efficient through microbiology, thus increasing growth, vigor, sugars and yields. Ok, so now you know what beneficial microbes are basically about – but let’s look a bit deeper!

The basic application of beneficial microbiology in soil and hydroponic gardening is simple, really. It kind of falls under the same concept as the food chain. When a plant’s root system has a well-rounded colony of micro-organisms, it has billions of microbes doing a wide range of jobs. Some microbes consume nutrients; some microbes consume the microbes that have consumed the nutrients, thus breaking the nutrients down into a smaller form. This allows the nutrient to be absorbed by the plant more efficiently. Other microbes defend against unbeneficial microbes and keep the plant’s natural defense system at its peak performance level. Each microbe exudes different types of enzymes, proteins, acids and other essential elements. These are the elements needed to break down trace minerals, micro nutrients, and macro nutrients making them immediately available as a food source to the plant. All this really means is an explosive increase in root mass, which equals increased nutrient uptake, which equals bigger yields!!!

So if these beneficial microbes are the building block to a robust and vigorous garden, how do we get them there in the first place? Remember, these little guys are living entities. So the best way to increase the levels of microbes in your gardening system is a fresh brewed, microbial rich solution. We are talking about Actively Aerated Microbial Extracts (AAME). Now, don’t switch off on me just because I’m using acronyms already. I’m telling you that AAMEs are going to change your life!  So listen up!

So What’s Brewing?

Actively Aerated Microbial Tea

Like I said, these little guys are LIVING so they’re going to need feeding. The idea behind AAME is to take an organic material that is high in beneficial aerobic microbes and add essential food sources to raise certain levels of each type of beneficial micro-organism. To get things to multiply, dissolved air and a food source in an aqueous environment is needed. But you have to create the right conditions for these little fellas to multiply at the rates we want – using water straight from the tap is a no-no (because of chlorine levels); reverse osmosis or de-chlorinated water at the perfect temperature and the right type of food sources will allow microbes to multiply at extremely rapid rates.

Beneficial Bacteria

There are three basic groups of beneficial micro-organisms (take note there are tens of thousands of individual types of each microbe in each group). The first to be addressed is beneficial bacteria, the smallest of the three groups. They attach to your root system and feed on unavailable nutrients in and around the root web. Once a bacterium has consumed a nutrient (food), the nutrient is then immobilized (locked inside of the bacteria’s cell wall).  Here the nutrient is broken down with a mixture of different proteins and enzymes. The only way that the nutrients can be unlocked (mineralized) and up-taken by the plant is if the bacteria dies and/or is consumed by a competing micro-organism. Once this process occurs, the nutrients are released in their mineralized form and are immediately absorbed by the plant.

Fungi

Fungi, the second group of beneficial micro-organisms, are much like bacteria in the sense that they too find and immobilize unavailable nutrients. Unlike bacteria, fungi find their nutrients in a completely different way. Fungi live in and around your root web, and grow miniscule root-like strands called “hyphae”; these strands can stretch for many feet. The hyphae stretch throughout the network of the plant’s root system, usually ending on an attachment site on the root. The nutrients are then distributed in a number of different ways. Immobilized nutrients are locked up within the cell walls of the hyphae until the fungal microbe dies and/or is consumed by a competing micro-organism. The nutrients then get mineralized and passed off to the plant as an “easy to absorb” food source. Other fungi trade exudates (carbohydrates, sugars and proteins made by plants and excreted by roots) for water and nutrients; these fungal organisms are known as mycorrhizae. Mycorrhizae work in a symbiotic relationship with the plant’s roots: the fungi brings nutrients and water back to the plant’s roots in exchange for exudates collected from the roots. It’s a win-win situation. The plant then becomes somewhat dependent on the fungi and the fungi cannot live without the exudates from the plant. Through this relationship, many different nutrients are mineralized and absorbed immediately by the plant.

Protozoa

The third type of beneficial micro-organism is the protozoa. Protozoa microbes can be up to 100 times the size of bacteria and fungi. The protozoa feed on mostly bacteria and fungi (protozoas can eat up to 10,000 bacteria a day). When the protozoa consume bacteria or fungi, they mineralize any of the nutrients that were immobilized in the bacteria or fungi. This unlocks any nutrients that have been locked up in the bacteria and fungi. They are then absorbed rapidly as a food source to the plant. Protozoa are at the top of the food chain in the beneficial microbe world. This means there always needs to be a food source, otherwise protozoa will die. Luckily, as the protozoa consume the microbes they consume small bits of organic matter that are processed and exuded as food sources for bacteria and fungi. This helps keep fungal and bacterial populations sustained when conditions are right. If fungal and bacterial populations diminish, protozoa will start to eat their own and eventually die. This is why it is important to replenish microbe populations with a balanced array of beneficial micro-organisms, keeping the food chain in balance and allowing optimal performance.

The only way to get an extremely high multiplication of micro-organisms is through a fresh extracted AAME. Unfortunately, Actively Aerated Microbial Extracts are not available as an ‘off-the-shelf’ product.  To solve this issue, an on-site extraction process with a culture of biology is necessary. This process can multiply the culture of aerobic micro-organisms over 9 billion times in a 24 hour period. When an AAME is used as a foliar spray and as a root inoculant, it will raise the number of micro-organisms that work together in a symbiotic relationship with the plant to increase vigor and yield. With a high diversity of beneficial micro-organisms, plants receive a wide array of the micro-organisms that exude humic, fulvic, amino acids and proteins. These micro-organisms and their exudates aid in immobilization and mineralization of trace elements, micro and macro nutrients.  Microbes have been around for millions of years and now we have the technology to put them to use in our gardens.

Microbe Tea – Q&A

You say actively aerated microbial extracts aren’t available ‘off-the-shelf’ – so once I’ve brewed the tea do I need to use it straight away?
No – think of it like milk. It will last for 12-24 hours if stored at room temperature, or 7-10 days in the refrigerator. Use the smell test. It should have an earthy and fresh aroma if it’s good. Smells damn awful when it’s gone bad!

How much microbial extract brew is good for my plants?
For Soil: Dilute with water at a rate of 75 ml to gallon (1:50). Apply this solution directly to your soil over the root zone.
For Hydro: Use the same dilution ratio but reintroduce more microbial tea solution to your nutrient solution every 7-10 days.

Can I use boiled tap water to make the microbial tea?
No, boiling won’t cut it. You must use non-chlorinated or Reverse Osmosis filtered water. Reverse osmosis machines are more affordable than you think. Check out the Small Boy made by Hydro-Logic.

What do you think about using microbes in your garden? Do you have any tips, tricks or stories to share?