In this article I will take you through how often to feed your fish, using auto-feeders, selecting the commercially produced feeds while accounting for feed composition, and some options for supplementing with home grown feed sources.

When and how often?

Fish tolerate a wide range of feeding schedules very well.  They actually adjust their metabolism to match food availability.  If you want your fish to grow quickly, or you have fewer than the recommended fish and need to produce more food for your plants, go ahead and feed them often.  Commercial aquaculture operations feed their fish as often as once an hour.  If, however, you are in an overstocked situation, or had an insect outbreak in one of your planting beds so you need to replant but only have small seedlings available, or for any number of other reasons, you need to “dial down” the amount of fertilizer your fish are producing, simply feed them less.  I often only feed my fish once a day, in the morning when I go to check on everything.  Sometimes, however, I’ll feed them again in the evening if I need to go to the greenhouse to pick some produce for dinner.

The best fish feeding rule of thumb is only feed your fish as much as they will eat within five minutes.  After five minutes, remove the remaining food from the tank with a fish net.  Soon, you will be able to judge just how much food to toss in, depending on your fish’s behavior at that moment, and you will no longer need to wait five minutes to see how much they eat.

The time you spend observing your fish when you feed them is very valuable.  Thus, you should avoid automatic feeders unless you are going on a short vacation and have no one to take care of your fish.  Automatic feeders aren’t inherently bad, but if your fish stop eating, something has likely gone wrong with your system and you will not receive this critical signal if you aren’t there at feeding time.  Fish may stop eating for a wide variety of reasons including water temperature being outside of “thriving” range, pH being outside tolerable range, too much ammonia and/or nitrites (a fish may have died in the tank giving off excess ammonia), too little oxygen, stress or a disease.  All of these are easily corrected if caught early, and potentially fatal if not.

Commercial feed

Tilapia Pellet

Commercially prepared fish feed is an excellent source of nutrition for your fish.  There are typically two types of fish feed sold in the U.S. – omnivorous and carnivorous – and they vary mostly in their protein content.  Within these types, you can select feed according to the stage of growth your fish are in.  Again, the formulation difference will largely be the amount of protein in the feed, although you will also notice a difference in pellet size.  Not surprisingly, as the fish get older, the size of the feed pellets gets larger.

Fish feed is comprised of proteins, fats, minerals, carbohydrates, and other nutrients that a fish in the wild would have in their normal diet, but that they cannot get in what is essentially a wet desert in captivity.   The sources for these nutrients are usually from fish meal, corn, soy, and other animal bi-products.

While we might find some of the ingredients in commercially available fish feed distasteful, one fish feed producer once described them to me as follows:

“For healthy fish, and in turn healthy food for people, these missing nutrients must be supplemented. Poultry meal provides about 65% protein and 6% calcium by weight. It also supplies about 4% phosphorus by weight and 19 important amino acids that tilapia and most other fish require for proper growth and reproductive functions. Poultry meal is poultry bone and meat that is cooked at extremely high temperatures before being added to the food mix. It is basically the equivalent of a ground chicken patty. Dried animal blood cells are just another way of saying hemoglobin. It is a highly nutritious, non-bovine ingredient that provides iron, phosphorus and many micronutrients that aid in oxygen absorption and gill health for the fish. Porcine Animal Fat is simply cooking lard (what makes pastries so “puffy” and flaky). It serves as a binder, a source of important fatty acids and aids in digestion.

Without these nutrients, the fish would have higher “bad” omega fatty acids and lower “good” omega fatty acids. A diet consisting primarily of soy, corn, rice and/or wheat will produce a fish that has significantly diminished health benefits for human consumption. This is actually a big reason why the nutritional value of store bought tilapia from overseas has been questioned so much recently by the media. Properly fed tilapias are a very healthy protein source.”

Kellen Weissenbach
Premium Fish Food

The protein in fish feed comes mainly from fish meal.  Fish meal can come from fishery wastes associated with the processing of fish for human consumption or from specific fish (herring, menhaden and pollack) which are harvested solely for the purpose of producing fish meal.

There is currently intense debate within the aquaponic and aquaculture communities about the wisdom of adding to the serious problem of over-fishing our oceans by feeding our farm-raised fish – fish from the ocean.  Thankfully, many experts are conducting ground breaking research to develop protein substitutes for fish meal.  An article in the Aquaponics Journal (issue #56, Q1 2010) highlighted three companies creating protein sources. At Ohio State University, aquaculturalists are exploring the feasibility of using soybeans to replace fish meal and plan to soon test the product on yellow perch. Scientists at the Agricultural Research Services and Montana Microbial Products have teamed up to produce a barley protein concentrate that can be fed to trout, salmon and other commercially produced fish. Finally, in Idaho Springs, Colorado, Oberon FMR has signed a deal with Miller-Coors to use 5,000 tons of beer sludge in combination with other ingredients to produce 6,000 tons of fish food flakes.

All fish feed, especially brands that use more natural ingredients and fewer preservatives, have a limited shelf life and are best stored in a cool, dry location.

Home grown feed

Duckweed Pool (image credit: David Hart)

Supplementing, or even entirely substituting your own, home-grown fish food can be personally satisfying, save money, and further decrease the environmental footprint of your aquaponics system by further closing the input loop.  The following is a list of some of the feed that can be easily cultivated for most omnivorous fish:

Duckweed –This fast growing aquatic plant doubles in mass every day when in its ideal environment.  In addition, duckweed is over 40% protein (more than soybeans) and efficiently removes contaminants from and adds oxygen to the water.  Duckweed grows best in dappled sunlight in relatively stagnant water with some fish waste.  The key is to keep it in a separate tank from your fish or they will just eat it all!

Worms - Earthworms, sludge worms, bloodworms, and composting red worms (AKA red wrigglers) all make excellent fish food.  The challenge is to grow enough of them to be more than an occasional, although probably very appreciated, treat for your fish.

Black Soldier Fly (BSF) Larvae – The Black Soldier Fly is considered a native of North America, and can be found in many parts of the United States. It is exceptionally active in the southeastern U.S. from April to November. Their grubs are considered beneficial scavengers in nature, and help to digest and recycle decomposing organic material including carrion, manure, fruits, and decaying plant waste. Their association to humanity is limited to compost piles, facilities producing manure, and poorly serviced toilets. Unlike the common house and fruit flies, they are not commonly found in association with humanity (picnics, kitchens, residential buildings, etc.).  While the mature fly has a short lifespan of only 5 – 8 days, the female can lay over 900 eggs.  Those eggs hatch in about 100 hours and, if conditions are right, will mature in 2 – 4 weeks.  During this stage, the larvae make excellent fish food, as well as robust compost consumers.  A product called the BioPod is specifically designed for BSF food composting and through clever design, has the added benefit of self-harvesting the larvae.

Other kitchen and garden scraps – Omnivorous fish like most bland-tasting, non-flowering plants and even some fruit.  I’ve found that my tilapia especially appreciate lettuce that is getting slimy and no longer fit for human consumption.  I’ve been told that they will eat untreated grass clippings (no weed killer or pesticides!).  They get very excited about the uneaten tops of strawberries.  Experiment!  If they don’t eat what you have given them in five minutes, and it is their normal feeding time, remove it from the tank and chalk it up to experience.  What have you got to lose?

I recommend that you consider any one, or a combination, of the feeds above as a supplement to a commercial fish feed.  Nutrition for living beings is a complex subject, especially in captivity. Just as we wouldn’t feed our dogs or cats exclusively a single, or even a couple foodstuffs, please consider feeding your aquaponic fish a varied diet that includes a reputable commercial feed.  Consider it a vitamin tablet for your fish to ensure that both they, and ultimately your plants, are getting all the nutrients they need.

Next months’ Aquaponics Explained article will be about Hydroponics vs. Aquaponics, and how they differ.

Words: Sylvia Bernstein, www.theaquaponicsource.com

“A man may fish with the worm that hath eat of a king, and eat of the fish that hath fed of that worm.”
~William Shakespeare.

Let’s hear it for worms! They not only help to increase the amount of air and water that gets into the soil, but they also play a key part in breaking down organic matter into forms that plants can use as food. And even if that weren’t enough, they also leave behind castings (worm poop) that rank as one of the most highly prized fertilizers on the planet.
Ask any seasoned organic grower (indoors or outdoors) and they’ll tell you that worm castings are where it’s all at. But why are they so special and what are the metrics of quality?

We decided it was about time we learnt more about worms and the rich, wholesome, soil enriching castings they produce so we brought in seasoned vermiculture expert, Larry Martin, to bring us up to speed on Mother Nature’s soil workers.

There are over 7,000 species of worms, but only two species, the Redworms (Eisenia fetida) and the European Nightcrawler (Eisenia hortensis) are widely used in vermiculture—farming worms and harvesting their castings and vermicomposting—using worms to create compost out of organic waste.

If you want to breed your own worms and create your own worm castings the first thing you need to do is look at  your chosen species of worm’s native habitat to get a good idea how they might function in a worm growing operation. Redworms and Euros are from the same genus and share a lot of the same traits, but they are actually different species.

Redworm Habitats

The redworm’s native habitat is on open grassland, especially where there is plenty of animal manure for them to feed on.  You will find these worms in great numbers on farmlands, particularly around animal pens and manure piles. The anaerobic bacteria in their manure is what gives it that distinctively unpleasant smell! The worms consume and aerate the manure, thus reducing the odor. They are top feeders that are found in the top 6-8 inches of the soil. Farmers that use pesticides will have very few worms and a very smelly farm.

Euro Habitats

The Euros native habitat is the forested areas of Hungary, but they are now found in other areas of Europe and the USA.  In Europe, due to their forest dwelling attributes, they are also known as the ‘leaf worm’, consuming the leaf litter and animal waste on the floor of the forests. They burrow much deeper than redworms and can be found up to three feet beneath the soil surface.
These two earthworms have a lot in common and can be raised together for home use in vermicomposting bins (more on that later).  It’s preferable to raise them separately if the excess worms will be sold.  The Euros are a larger and tougher worm, which makes them a great worm for fishing as well as for vermicomposting and gardening.  The redworms breed quickly and produce more offspring than Euros but, pound for pound, Euros consume more organic matter than redworms.

How Worms Work

Earthworms have no teeth, but daily they consume their own weight in decomposing organic matter and microorganisms, from which they derive their nutrients. The crop and gizzards help breakdown their food, and astonishingly, worms have five hearts to pump blood throughout their body. Worms breathe through their skin and must live in a moist environment. As organic matter passes through a worm’s intestines, it becomes inoculated with many more microorganisms.
A worm ‘cast’ is produced after a worm feeds. This worm poop is rich in nutrients and beneficial soil bacteria. On the way through the worm’s body, the calciferous gland coats each tiny casting with different thicknesses of calcium that are readily available for the plant to uptake.  It is the multiple layers of calcium that make worm castings a sustainable slow release fertilizer.  This encapsulates all the plant nutrients and microorganisms with the correct amount of moisture that will keep the nutrients and microorganisms viable for up to three years when stored properly.

General Earthworm Anatomy

Both species are true hermaphrodites.  The smooth band or “Clitellum” near the head end of the worm is formed at maturity. On the underside of the Clitellum there are two pores that release the sperm on one side and two pores that release ovum.  They mate head to head so both can share the sperm and ovum.  They also secrete albumin (a water soluble protein) to feed the developing baby worms within the cocoon, and mucous to make the protective cover around the cocoon.  The cocoons can stay dormant and remain viable for a year or more and will not hatch until the right moisture, temperature and the proper microorganisms are present. Given optimal conditions, a cocoon will hatch in a couple of weeks and produce one to four small pinkish baby worms about ¼ inch long. Given the right conditions, it takes them three to four months to reach maturity.

Vermicompost and Worm Castings  – Know The Difference!

The vermicomposting process greatly reduces the volume of material in the finished product.  For example, 20 cubic yards of compost or compostable organic matter processed through the worm would reduce the volume to between 10 and two cubic yards of a much denser finished product – Vermicompost, not pure worm castings.

So what actually is the difference between vermicompost and worm castings?

Vermicompost is the end product of adding worms to decaying plant debris to speed up the process of breaking down the organic matter (compost).  After removing the worms from the process, what remains is the vermicompost.  Vermicompost will have typically not been screened and not all of the organic material will have passed through the worm.

Worm Castings (aka ‘worm humus,’ ‘worm manure’ and ‘vermicasts’) are literally worm poop that has been separated from vermicompost by passing it through a 1/8th inch screen.  All of the organic matter that has not passed through the worm is removed, leaving just worm castings.

A really good Vermicompost will contain 40 to 60% pure worm castings, but many products out there contain significantly less. Much like thermal compost, vermicompost is a highly variable product. Some manufactures add pure worm castings to cured compost, this is slightly different and is called a blend. The advantage of a blend is you know the percentage of both the castings and the compost that is being purchased. As with any product, it’s always advisable to do some research before buying vermicompost to ensure you are purchasing a good quality, effective product.

Doing it Yourself with Vermicomposters

Also known as a ‘worm bin’ or ‘wormery’, a vermicomposter is a vessel in which vermicompost and worm castings are produced. There are many types of contraptions in which worms can live and produce valuable plant amendments; they range from huge worm bins used in commercial production, to small plastic boxes you can use at home.

Worm Bin Tips

A simple worm bin can be purchased online or you can easily use your DIY skills, purchase a similar bin or tote from a DIY store and make your own. If there is a strong chemical smell coming out of the bin you will need to let it air out for several days or fill it with water and place in the sun for a couple of days.  The pliable plastic bins contain chemicals that leach out which will slowly kill the worms! Any of the food grade plastics will not harm the worms. It’s a good idea to drill 12-15 ¼ inch holes in the bottom to allow air flow.

The multiple stacked vermicompost bins look quite glitzy, but they can have a high failure rate if Redworms are used because they often drown in the reservoir at the bottom of the unit. Also, worms have a mind of their own and it is usually hard to ‘train’ the worms to migrate to the upper tray.

A larger ground vermicomposting bin can be made from 2×12 lumber or cinder blocks. For a bin that would deal with a family of four, simply make a raised bed that is 2 feet wide by 3 feet long with weed block placed on the bottom—this will help to keep the moles from dining on your worms. In-ground worm bins should be located in partial shade to avoid temperature extremes.

In any worm bin, a combination of the Redworms and Euros work very well together.  The Redworms are surface feeders and the Euros feed both surface and subsurface.  The main difference between the two species is that the Redworm still has an aquatic gene that attracts them to the water. If the mix of materials becomes too wet in the vermicomposter, they will preferentially stay in the water and die in less than 24 hours.  Other than checking the moisture content, you can tell if the mix is too wet – dead worm odor is really, really nasty.

Some worm bins have a reservoir and tap in the bottom to catch and pour the “worm tea”. A lot of this liquid is from the fresh fruits and veggies that are 90% water.  Some of the directions sold with the bin encourage the use of excess water to make ‘worm tea.’ which at that point is actually ‘garbage tea!’  Tea is best made from the finished vermicompost or worm castings, which when applied will not burn the plants.

Bedding

The first step is filling your worm bin half way with ‘bedding’ – brown (carbon) coarse organic matter to trap oxygen below the surface. The best bedding is made with stuff taken from your own compost heap. Bedding materials such as shredded paper and/or cardboard that is commonly used will pack too tight and cut off the oxygen needed to sustain healthy worm populations.  However both may be used in moderation in combination with the following materials:  Pine shavings from rabbit cages or horse stalls, chopped woody plant stems from the garden and shredded dead small branches.

Tip: Do not use any cedar shavings or pine straw in bedding mixes as they are high in harmful resins.
After adding your bedding to the worm bin, water well to make sure that there are no dry spots.

So What do Worms Like to Eat?

Use a mix of green veggies waste from the kitchen or garden, plus fruits, grass, etc. for your nitrogen source.  Do not overload it with any one item.  It is ok to use citrus waste, but don’t go to a juicer and put a ton of it in at a time.  Do not use meat, cheese or other milk products, these take too long to break down and will encourage animals to dig up your worm beds. The wastes should be chopped up so it will break down quicker.

The quality of the vermicompost can be improved with the addition of a tablespoonful of a quality rock dust once a month.  Microbial inoculants are also a great additive to increase the microbial population and rapidly break down the organic matter, as well as to help convert the rock dust to usable minerals for plant uptake.
Remember, what is grown in our earth can be recycled through our earthworms and returned to Mother Nature.  Be aware that feedstock used from municipal composting operations may contain heavy metals, pesticides, herbicides and sometime sewer sludge.  Leaves and twigs picked up by the city curbside programs often have traces of antifreeze, oil and other contaminates from the roads. The worms do a great job reducing contaminates, but do not complete eliminate them. If you put garbage into your vermicomposting you will get garbage out of the back end of those worms!

Buying worms – Buyers Beware!

Try to find someone locally that is vermicomposting and purchase worms from them. If that doesn’t work try the Internet but do some checks to make sure that this person has been in business for more than a week. Worms are usually purchased by the pound. Sounds simple enough, but there are some different opinions in what constitutes a pound of worms. Some will include the weight of the bedding in the pound of worms. But a pound of worms should be just that – one pound of worms. This includes the ¾ to 1 pound of bedding that is mixed with the 1 pound worms to keep them alive while in transit. The rule of thumb is to purchase ½ to 1 pound of worms per sq. ft. of your vermicomposting bin.
Next, put the worms to work. A mixture of the worms and their bedding is great way of inoculating the garden, planter box or other growing containers. The partially vermicomposted bedding will give the plants a shot in the arm.  The worms will start to work aerating the soil and converting the organic matter to the nutrients NPK, Calcium, Iron, etc., plus microorganisms need for a healthy soil food web.

A Quick and Easy Worm Tea

Place two cups of vermicompost in a recycled milk jug(s), fill with water and shake well several times during the day. The next day it is ready to use. When using this tea for recovering stressed plants, shake the tea well before watering. When applying to healthy plants simply watered with the clearer tea leaving the debris in the jug. Alternatively you can pour the clear liquid through cotton or cheese cloth filter into a spray bottle, this solution can then be used as foliar spray which will give the plants a boost of nutrients, and populate the foliage with beneficial bacteria to help protect against pests and disease.

Tips & General info:

Beneficial Biology: A good quality vermicompost with have a minimum of the following microbes; Aerobic & Facultative Bacteria, Yeast, Actinomycetes, Pseudomonads & Nitrogen Fixing Bacteria. Do not dry out the vermicompost. 30 to 40% moisture content is necessary to maintain micro-life of product. Do not freeze as it will kill most all of the microbes and storing above 100 degrees will also have a deleterious effect.

Nutrients: Calcium, Magnesium, Nitrogen, Phosphate, Potassium, Manganese, Boron, Iron & Zinc. Hopefully it will be very low in the heavy metals and free of E. coli and Salmonella. Some really great quality vermicompost contain less heavy metals than in some municipal drinking water systems!

Application Rates: For good quality Vermicompost, use 15-25% as a soil amendment for growing veggies and up to 30-40% for plants with a higher nutrients demand such as fast growing annuals, trees and shrubs. For large outdoor plots use two tons per acre or 80LB per 1000 ft2. If using high quality worm castings, use 50% of the above recommendations.

Teas: Generally speaking aerobic teas made using a quality vermicompost are often superior to that of aerobic tea made with only thermal compost. However, teas made with only vermicompost will more often than not be dominated by bacteria and low on fungi. The best approach for a diverse range of soil food web organisms is to use both types of compost as a microbe source.

Consumer Quality Control Test:

Use empty 20oz. drink bottles
Place 3oz. of worm castings in each labeled test bottle
Fill each bottle about ¾ full of water.
Shake vigorously for two to three minutes
Let is set for 25 or 30 minutes
First, check to see what if anything is floating on the surface. This is a good way to check if there are any weed seeds and how much unconsumed junk is floating.
Next, check out the sediment layers. If they use sand as filler, it will be the first to settle out at the bottom. What is the color of the layers? The darker the color the more pure castings will be in the product. This is my type of testing, it costs you only your time!

Purchasing Tips:

When purchasing vermicompost, make sure that the bag is not air tight. Invariably the vermicompost will have some worms and egg cocoons, which will hatch. They require a lot of oxygen as do the microorganisms. Without some air flow they will die and really smell bad. Pure worm castings have a shelf life or around two years, after this the micro-life will begin to diminish.
When buying worm castings for the first time, ask the retailer if you can open up the bag. There should be a pleasant earthy odor and a nice uniform texture, much like coffee grounds. The color of the castings should be should be light to dark black.

“Life is hard. Then you die. Then they throw dirt in your face. Then the worms eat you. Be grateful it happens in that order.”
~ David Gerrold

Words: Larry Martin

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

WORDS: Simon Hart

Give The Worms Some Credit

We all want to use items that increase our garden’s fertility in the hopes of explosive yields. With that as our aim, there is one item that stands out as a must-have for all soil and soil-less gardens: worm castings. Vermicomposting is the use of worms to break down organic material. Worm castings are the result of their digestion process. This process will give you some of the highest quality castings available and help you create a more technical and successful garden experience without a lot of effort.

Current research show extremely complex benefits from the use of worm castings in agriculture. A green technology, vermicomposting is the epitome of reduce, reuse, and recycle. Research continues and our knowledge of these unsuspecting creatures in the soil shows a fascinating connection between the worms and overall ecosystem health. Their effects on soil biology, nutrient availability, and the complexity of their decomposition of organic materials are just some of the things being studied. Although we are just starting to understand the relationship between earthworms and healthy soils, worms have been fascinating people for millennia.

Cleopatra, queen of the Nile, decreed that worms were sacred and were not to be harmed. The Greek philosopher Aristotle declared them to be the guts of the soil. The great biologist, Charles Darwin, who may be best known for his theory of evolution, started his scientific work looking at earthworms. In fact, he spent the latter part of his scientific career looking at nothing but earthworms at Down House, his country estate just outside of London. He was fascinated by them and utterly convinced that worms were among the unsung heroes within the natural world; in 1881 he published his life-long research on earthworms. In one project detailed in his work, he took small coal stones, spread them over a field, and left them for 20 years. He then dug a trench to see how far down the worms had moved the coal. Talk about long-term research.

WORM WISDOM
Worm castings are an amazing soil amendment, but go easy on them! They typically contain 5 times the normal levels of nitrogen found in regular soils, 7 times more phosphorus, and 11 times more potassium! Worm castings also contain calcium, magnesium and other micro-nutrients as well as tons of beneficial organisms and microbes that help to restore soil life and begin recreating the soil food web. Worm castings rule!!

The Knowledge

The industrious nature of worms is a power that can be unleashed on all unsuspecting gardens. While all urban gardeners are familiar with worm castings, most buy their castings at their local shop because it is very convenient. But given just a little space, time, and knowledge it is possible to grow your own castings. Not convinced that it’s worth the effort? Have a look at the benefits and then the actual work involved in growing worms and supplying your own rich, microbial super-charged soil amendment.

Research shows that vermicompost stimulates plant growth even when plants are already receiving optimal nutrition. Improved seed germination, accelerated growth and development, and increased productivity and yield are all scientifically validated claims. There are new theories, such as the possibility of transient plant growth regulators being absorbed by the humates which form in rich worm castings. Other benefits, such as disease prevention and the ability to repel pests, are possibilities, but there needs to be more study to understand the mechanisms behind these potential benefits.

When compared to regular compost, vermicompost stands out as the winner. Higher levels of plant-available nitrogen, phosphorus, potassium, sulphur and magnesium make vermicompost nutritionally superior. Microbiology is also more complex in vermicompost than standard compost. Why? First, vermicompost is processed at a moderate temperature range that never comes close to the140 degrees Fahrenheit (60 degrees Celsius) or higher achieved in thermophylic digested compost. This means that your worm castings will have more microbes meant to live at normal temperatures when compared to compost. Although the process is not entirely understood, it is also clear that worms release more microbes than they ingest, meaning that they are actually creating microbes during their constant eating.

Many composters will tell you that you need a thermophylic reaction (140 degrees Fahrenheit / 60 degrees Celsius or higher) or pathogens will not be destroyed. Research has shown that castings produced in pathogen-rich environments, such as human biosolids (I’m glad I don’t research sewage) contain no pathogens. Dissections show that something happens within the first quarter inch (5mm) of the worm that completely removes pathenogenic substances. That being said, I do not recommend that any gardener feed their worms biosolids.

There are estimates that there could be over 1,800 species of worms worldwide. Many of the worm casting available in retail shops are produced by African nightcrawlers. However, for the urban gardener looking to start vermicomposting, this is probably not the right choice of species due to its specific growing requirements.

Eisenia Fetida, more commonly known as a Red Wiggler, is indigenous to most parts of the world. This particular worm is extremely tough and adaptable, able to handle a temperature range from 32-95 degrees Fahrenheit (0-35 degrees Celcius), and the eggs or cocoons can survive short periods of complete freezing. This species is commonly used in commercial vermicomposting and is easily accessed by hobby gardeners through Internet sales. Before you order your worms, you had better have somewhere for them to live. There are many small home-sized worm farm units available. Some are more efficient and complicated than others. Remember that vermicomposting is a type of farming, not an industrial process, so bigger isn’t necessarily better. A savvy gardener will want to master the basics prior to a significant investment in equipment.

The Experience (in brief)

My first experience with vermicomposting began last year when, to the horror of my colleagues, I placed a worm bin in my office. My boss was quick to inform me that if it started to smell that would be the end of it. The pressure was on, so I put in my bedding and a half pound of worms and started the feeding frenzy.

I placed approximately 44 pounds (20 kg) of food waste in the bin over 14 weeks. I was amazed at how quickly the worms processed material and everyone in the office was stunned that there was essentially no smell other than a mild earthy aroma. This first batch of quality vermicompost got me hooked, and I would like to pass this concept along as a suggestion from one gardener to another.

I have moved on from my office bin, which in the end was too small. I am going to move my worm adventures outdoors into a very straightforward continuous flow wedge. Essentially I am going to build a three-sided open-end structure made from straw bales. To begin, I will add material and then worms against the back wall. After that I will continue to put in bedding and food sources. Once the pile reaches the open end I will take the straw bales from the closed end and move them to the open end. At this point I will harvest the oldest material to use as vermicompost and begin moving the pile in the opposite direction. This will get rid of the issue of removing the worms from my compost because they will move into the fresh material as you take away the digested castings. This was an issue with my office bin where I had to take the castings out and create small piles, then remove the top layer as the worms retreated to the base of the piles. Follow this with taking the base of each pile (which contains most of your worms) and put it back in the bin with fresh bedding and food. You can always buy new worms every time you renew your bin, but this adds cost to the exercise. That money can be better spent on other things by keeping your worm population healthy and productive.

Giving Your Worms a Home

To manage your worms properly you need to consider five essentials:

1. A hospitable living environment: the best worm farms have the best bedding. Things like straw, peat moss, coir, newsprint, cardboard and even dried leaves all make excellent bedding and can provide different benefits when blended together. You are looking to create a moist environment with lots of air pockets and a high carbon to nitrogen ratio. I have found a blend of straw and coir to be an excellent mix. A pH range of 5-9 is acceptable with a level of 7 being ideal.

WORM WISDOM
Adding grit to your bedding can help worms process more material. Inputs such as soil, powdered limestone, rock dust, egg shells and zeolite can provide this abrasive material that worms use in their gizzards. Note that all of these items will also provide extra benefit when added to your soil-less mix as well.

2. A good food source: worms are what they eat, so your food source is very important. Vegetable and fruit peelings are excellent, and coffee grounds are great when available. Kelp meal is a good choice, but remember that worms are sensitive to salt. Corrugated cardboard is also a good food source because of the high protein glue used to bind it. Commercially, there are many more food sources, including manures; but for the urban gardener it’s fine to stick to what you might put in a standard compost bin.

3. Adequate moisture: worms need a damp environment to get the job done and be happy while doing it. The moisture content in the bedding should be somewhere around 70-90 percent. This means you may have to add water at the start, but as you pile the kitchen scraps into the bedding the moisture should balance out to a good range.

4. Worms need to breathe, so make sure there is a good level of oxygen. If bedding becomes too compact it will force worms out by creating an anaerobic environment, which kills worms and will smell like something you don’t want in your garden.

5. Protection from extreme temperatures. The Red Wiggler is a perfect worm for vermicomposting because of its temperature range. However, you need to keep direct sun off your bin or pile because it can overheat the environment. Remember, also, that direct sun is toxic to worms. Outdoor vermicomposting does require some shelter planning, especially in Canadian winters that sometimes spill into the northern states too.

WORM WISDOM
Space is premium in small urban gardens, but many worm bins are small enough to fit under the kitchen sink or under your flood table. Most common small units use a top feed bed where you are adding food material into the worm bedding as it becomes available. Looking to upgrade? Consider a vertically stacked tray system for even more castings out of the same area.

The Reward

So now you want to use some of the black gold that has been growing in your worm bin. The finished product will range from 10-50 percent of the original weight of the material. But don’t worry because the best ratio to mix into your growing medium is about 10 percent. You can add up to 40 percent, but using over 40 percent seems to decrease its value, and castings can then actually slow the growth of plants. Use it as a top dressing or mix it directly into your medium. As a growing tip, if you are simply looking to enhance the microbial diversity in your rhizosphere, then consider the use of an aerobic compost tea to enhance the levels of various bacterial species. Remember that vermicompost has a much broader diversity of microbes than standard compost, and they reproduce rapidly at room temperature, so to use it in an aerated tea is an exceptional way to stretch its value in your garden. Without question, the addition of worm castings provides urban gardeners with accelerated plant growth. And to those urban gardeners up for the challenge, small-scale worm farming produces a growth accelerator while decreasing the waste that leaves your house for the landfill. I hope that you see some of the benefits now, and will experiment to bring vermicompost into your urban jungle.

Simon Hart is the senior technical advisor for Grotek Manufacturing in Canada. If you have any questions regarding vermicomposting or anything else garden-related, post them below!