Aquaponic Food Production for Long Term Survival, by Stone of Scone

Tuesday, Jul 19, 2011

Food storage is important for short term survival, and everyone should have at least a six months to a multi-year food supply. But long term survival requires that you grow your own food. Whether it is TEOTWAWKI or just losing your income because you were laid off from your job, a home food production system is essential to your security.

Most successful food production systems involve using a greenhouse for year round food production, as a greenhouse extends the growing season, and shields your crops from severe weather. Another advantage is that a greenhouse is better protected from nuclear, biological, and chemical warfare than open field farming. And a greenhouse has greater physical security than an open field against pests and animals that might want to share in your harvest, whether they have four legs or two.

One problem with a greenhouse is providing an efficient watering system that doesn't require you to hand water your plants, and that will reclaim the run-off or excess water that would otherwise be lost into the floor of the greenhouse. Water is always an expense, and if your city water supply or electric powered well pump is not working, then it would be almost impossible to manually haul enough water by hand to maintain your greenhouse plants. Another problem is how to keep the temperature of the greenhouse stable without using propane or electric heaters. A greenhouse needs to store the heat collected during the day, and slowly release this heat so that the plants won't freeze when the sun goes down. I believe that the concept of "Aquaponics" solves both of these problems, and is the perfect technique for growing food off the grid in a greenhouse.

Aquaponics is a combination of Hydroponics (growing plants in water), and Aquaculture (growing fish in water). Aquaponics uses low energy water pumps to move the water from the fish tank through a gravel-filled bed to filter the water for the fish, while providing water for the plants growing in the gravel bed. The low pressure water pumps recycle the water for continuous use, and require a very small amount of electricity power which can be provided by a solar panel.

The fish in an Aquaponic system are a good survival protein source, but more importantly the fish create ammonia as a waste product, which provides fertilizer for the plants. The fish ammonia is converted into liquid nitrate fertilizer by autotrophic bacteria that reside in the gravel-filled growing beds, which is where the plants are raised. The water pump moves the water from fish tank into the gravel filled grow beds and back to the fish tank, thereby watering all of the plants automatically, while purifying the water for the fish by removing the ammonia. Around 98% of the water is conserved and reused, with very little makeup water needed. This solves the large water consumption problem that most greenhouses have. And, the large amount of water contained in the fish tank (ours has nearly 1,000 gallons) acts as a temperature buffer, which moderates the daily swings in temperature in the greenhouse by storing the excess heat during the day, and gently emitting the heat each night to keep the plants from freezing. The thermal storage capacity of the water based Aquaponic system fully complements any "Solar Greenhouse" design.

Aquaponics produces a large amount of organically grown food, as much if not more than a standard hydroponic greenhouse, without purchasing any hydroponic chemicals. Once you have the system set up, it pretty much runs itself with much less effort than traditional gardening. And if you can grow your own fish food from duckweed, black soldier fly larvae, earthworms, crickets, etc., then the system becomes almost completely self contained.

Our setup is pretty simple, and cost around $1,500. We built a small greenhouse frame using recycled wood. Inside we built our Aquaponic structure that is 8' x 8' wide and 8' tall. The foundation of the structure is an 8' x 8' wide by 2' deep fish tank made out of 2x12 lumber lined with a 12 mil rubber liner, all of which rests on concrete blocks. Above the fish tank are 4 gravel filled grow-beds mounted on 8' tall 4x4 posts. The grow beds are wooden boxes made from 2x12 lumber that are 8' long, 2' 6" wide, and one foot deep. The grow-beds are spaced 5' and 8' off the ground directly above the fish tank, mounted on top of each other like bunk beds with a walkway between them. Since the grow-beds are only 2' 6" wide, there is room between them for a 3' catwalk over the fish tank to let us stand and work between the two sets of stacked grow-beds.

There are a lot of ways to build a cheaper aquaponic system. Once way is by using recycled plastic barrels for the fish tanks, and making the grow beds by cutting plastic barrels longways and laying them on their sides on a wooden rack and filling them with gravel, and then plumbing everything together with PVC pipe. You can also do it on a small scale with a standard aquarium and small water pump to push water through your potted plants on the windowsill, as long as you have a place for a "biofilter" such as a gravel filled bed or refugium where the bacteria that changes the ammonia into nitrogen can reside.

A working "biofilter" is the key ingredient to a good aquaponics system, as the bacteria in the biofilter keeps the fish water clean, and changes ammonia into nitrogen for the plants. The bacteria need to reside in a wet environment that has plenty of oxygen, and little or no light. A gravel bed that is alternately flooded and drained, is perfect for this type of bacteria to thrive in. Other aquaponic solutions, such as Nutrient Film Technique (NFT) and Deep Water Raft Technique, use a large amount of netting submerged in the water to give a place for the bacteria to reside. We chose a grow-bed filled with 1 foot of gravel as our biofilter, as it is simpler to build.

The bacteria in the gravel biofilter changes the ammonia into nitrogen in two steps. The first step is performed by the Nitrosomonas bacteria, which changes the total fish ammonia (NH3 and NH4+) into nitrite (NO2). The next process is accomplished by the Nitrobacter bacteria that changes the nitrite (NO2) into nitrate (NO3), which the plants use as fertilizer. The ammonia and nitrites are very toxic to fish, while the nitrates are fairly harmless, so it is important to monitor the bacteria by testing the water quality using the inexpensive aquarium test strips sold at any pet store. As long as you have a large amount of gravel or other media for the bacteria to colonize, your water quality won't be an issue. If you are using sterile media, you won't have any bacteria to start with, and you will need to purchase the bacteria from an aquarium shop or from Fritz-Zyme. We used gravel from a creek, as the Nitrosomonas and Nitrobacter bacteria is always abundant in river gravel. Since these two types of bacteria work in tandem and do not reproduce quickly, it may take anywhere from 2 to 4 weeks to ramp up the bacteria to full production. So, it may important not to add a large number of fish at the same time unless you already have a good supply of bacteria at work in your system.

Our first step in construction of our Aquaponic system was to lay an 8' x 8' "carpet" of around 40 concrete blocks for the foundation of the fish tank. It took a long time to get the blocks level using a spirit level and a long 2x4, but this is probably the most crucial part of the construction. The next step was to build the fish tank out of wood, that would ultimately be fitted with a rubber liner. I created a square box out of 2x12 lumber standing on their edges, that was a little less than 8' x 8' and held together by wood screws. I designed it so that the 2x12's had an extra 3.5" overlap or "flap" on each of the corners, so I could drill holes and put carriage bolts through the 4x4 posts and 2x12 sides from two different directions on each of the outside corners. This holds the wood seams together. It is very important to "overbuild" the tank seams on a wooden fish tank with carriage bolts, wood screws, etc. as the water pressure is very great. Once I had my square box built, I made sure it was perfectly "square" by measuring the distances diagonally across from each corner. When these two distances were the same, I knew it was square. Then I covered what was to be the bottom of the tank with 8' long 2x4s, nailed into the 2x12s with a 2" gap between each 2x4. When I turned the 8'x8' box over and placed it on the concrete block foundation, the gaps between the 2x4s allowed me to put shims between the blocks and the 2x4s, so that each concrete block was helping to evenly support the 2x4s that held up the fish tank.

For the bottom of the fish tank, I nailed an 8'x8' section of heavy duty 1" flooring over the 2x4s that were shimmed against the concrete blocks. The next step was to secure the second set of 2x12s standing on edge on top of the first set, to bring the fish tank up to two feet in depth. I again secured it to the 4x4s with carriage bolts in all of the corners, all the while making sure the 4x4 posts were plumb. Copious amounts of wood screws were added wherever possible. After this I inserted the rubber liner to make the tank hold water.

I calculated the weight of the water in the tank as follows: 8' x 8' x 2' equals 128 cubic feet of water, times 7.5 gallons per cubic foot, equals 960 gallons of water. With around eight pounds per gallon, this would give a total of 7,680 pounds of water, not to mention the gravel beds. So, I am giving a lot of detail on how to over-engineer the fish tank, as with this much weight and water, there will be no small failures, only big ones.

Now this is a very large tank, and as you can always add more grow-beds or an NFT system to the tank, but it is not so easy to add another fish tank that is incorporated with the pumps into the same aquaponic system. The general ratio from the research I have read is that you can use 2 cubic feet of gravel growbed for each cubic feet of water in the fish tank. Since I plan to feed my family off this system, I thought it was better to start with a moderately large fish tank, and then add more grow beds later. And, the larger your tank, the less problems you will have with any rapid changes in temperature, pH, Ammonia, or other problems. A larger tank with over 500 gallons of water buffers most problems, and gives you more time to find a solution and correct it.

The construction of the grow beds was much easier, as there were no real water pressure issues. I nailed 2x12s to the upright 4x4 posts to form boxes that are 8' long, and 2'6" wide. For the bottom of the grow-beds, I nailed 2x4s laid on their sides, and covered them with 1" flooring, topped off with the same 12 mil rubber liner I used on the fish tank, which I purchased at FarmTek.

The next part was the plumbing. I used rubber Uniseal bulkheads to hold the 1" PVC pipe straight up for a stand pipe drain in the bottom of each grow bed. The Uniseal is great, you just drill a hole with a hole saw through the rubber liner and 1" flooring in the growbed, and insert the rubber Uniseal bulkhead, and then slide the PVC pipe through the bulkhead. The 1" PVC pipe is a tight fit, but there are no leaks, and you can pull the pipe out later if you have a problem. To keep the gravel away from the stand pipe, I used a 3" PVC pipe about 8" long that I drilled with about 50 ¼" holes and nested the 3" pipe around the 1" standpipe.

By stacking the grow-beds on top of each other like bunk beds and placing the inputs and drains on opposite ends, and I make the water traverse the entire length of each of the two gravel-filled grow-beds in the stack before it can return to the fish tank. I use two 330 gallon per hour fountain pumps I got from Lowe's to pump water to the top growbed. Since it takes about 15 minutes for the grow-beds to fill up, and about 45 minutes for them to drain, I set a timer that runs the pumps for 15 minutes on the hour. This gives me the "ebb and flow" water system that is crucial to aquaponics. Each growbed needs to fill up with water to irrigate the plants and the bacteria for the system to operate. But each growbed also needs to dump all of the water back out, so that oxygen can reach the plant roots, and the bacteria can function. If you don't drain the water, you will have an anaerobic condition (no oxygen), and your plant roots will die and harmful types of bacteria will begin to develop.

One way to create an "ebb and flow", or "flood and drain" cycle is to use a Bell Siphon, which will automatically siphon all of the water out of the grow bed once it reaches a certain depth. Bell siphons are widely used in Aquaponics, and the University of Hawaii has a good research PDF on how to build one. However, the bell siphon can malfunction, and they assume that your water pumps will run continuously. That is, with a bell siphon, if your pumps quit working, you may end up with a grow bed half full of water and no drainage. I opted to build something simpler, with just a 6" long stand pipe out of 1" PVC, with a ¼" drain hole just above the bulkhead. The stand pipe is the main drain pipe, that sticks straight up and keeps the water from ever cresting higher than 6" deep, as it will just flow into the pipe. The ¼" drain hole just above the bulkhead keeps a continual drain going, but the amount of water it relieves is less than the 330 gallon per hour pump is putting into the growbed. So, after the growbed fills up and the water crests over the standpipe, the timer will shut the water off and the rest of the water will slowly flow back out through the ¼" hole at the bottom of the standpipe. I found this approach to be more energy efficient for an off-grid system, and the water retention period in the growbeds is long enough for the ammonia-eliminating bacteria to function completely.

Using "free" river gravel for the media in the grow bed is the cheapest option possible, but other media options are vermiculite, perlite, expanded clay balls (which are sold under the trade names of Hydroton and LECA for Lightweight Expanded Clay Aggregate), and coconut fiber, which is also called "coir". We have tried adding a layer of coir over our river gravel, and found that it makes it easier to start the plants from seed over planting directly in the river gravel. The coir does not deteriorate, is PH neutral, and wicks the water up to keep the seeds moist for germination. You can get 35 pounds of coir in compressed bricks from Terra Prima Industries for around $70 with shipping.

Fish selection is another topic for Aquaponics. Tilapia are the most commonly used fish, as they are herbivores that eat algae and aquatic plants, grow very fast, handle crowding well, and are very prolific breeders. Tilapia are mouth-brooders, and raise their young inside the mother's mouth. Tilapia have a lot of advantages, but they cannot handle cold water. The White Nile Tilapia, which grows the fastest of the species, will show stress at water temperatures less than 62 degrees, and will die at 55 degrees. The Blue Tilapia is the most cold tolerant, but will die at temperatures less than 50 degrees. Tilapia really need 80 degree water. If you are off the grid in a cold climate with Tilapia, you will need to find a way to heat the water to these temperatures, year round. This means some sort of solar thermal panel that will thermo-siphon or otherwise pump hot water up to the fish tank. Fish cannot handle thermal shock or any quick changes in water temperature, so you will have to construct some sort of heat exchanger that can fit inside the fish tank. This adds a lot of complexity to an off grid food production system.

For this reason, I chose to go with Bluegill, as they can handle water temperatures down to 39 degrees, and the greenhouse always keeps the water at least that warm without assistance. Another reason I chose Bluegill is that they are much cheaper than Tilapia, as I cannot get Tilapia locally. The "Tilapia Source" is a great company to work with, but they would have to overnight them to me for $70, plus charge $2 a fish – for a total of $170 for 50 Tilapia fingerlings. Instead, I bought 100 Bluegill for only $40.00 from Farley's Fish Farm from their truck that came to our local Farmer's Co-Op. Farley's serves about 12 or 13 states here in the Southeast USA, and I found them to be a very reasonable resource for fish.

Bluegill is a good fish for Aquaponics, as they handle crowding well, can tolerate various PH and other water quality issues, and do not generally eat each other. Other fish used in Aquaponics are Catfish, Yellow Perch, Bass, Koi, Goldfish, and sometimes Trout.

I had a minor problem in the beginning with a fish disease called "Columnaris", which I diagnosed from from a "Fish Pharmacy" web site. Columnaris is a small white growth that occurs on the fins. The Fish Pharmacy web site had a toxic pharmacy solution for every fish problem. However, in Aquaponics you are not going to be able to treat the fish with anything that is not organic, or that you would not eat yourself. This excludes all of the anti-fungal treatments, or any medicine that contains some type of poison. Even the regular antibiotics that are meant for fish are not meant for humans to eat, and need to be excluded. I found from research on the web that Columnaris responds well to the addition of salt and other minerals to the water, on the order of 1 tablespoon for every 50 gallons of water. For my setup, I put over a cup of sea salt into the water, and the disease has began to retreat, with only one fish still showing signs. Columnaris is in almost every fish tank, and probably came in with the fish, or in the river gravel I used. It finds an opening when the fish are mishandled in some way. My mistake was to not acclimate the temperature of the fish when I brought them home in a bag from the fish truck, which created a lot of stress. We should have let the bag float in the water for 15 minutes before letting the fish out. The thermal shock and other rough handling I did on day one is probably the reason for the Columnaris problem. But since I only had to add sea salt to the fish tank to correct the problem, I will have no worries about eating the fish at some point. I can discard any fish that show signs of Columnaris, if they still have that problem when I harvest, and only eat the best. I know exactly how these fish have been raised, and what has gone into them, which is much better than what you buy at the supermarket. But what I find most reassuring about raising and eating fish I raise is that when the fish are eaten fresh, there are very few diseases that fish have can be passed on to humans, unlike the trichina worms that pigs can give to humans, tularemia in rabbits, tetanus in horse meat, etc. These diseases can kill you if you live in a time without access to modern medicine. Columnaris won't hurt humans, and aquaponically raised fish will not generally have diseases that affect humans, and so are a very healthy source of protein.

But the real purpose of the fish in Aquaponics is not just for food, but to provide the ammonia to power the bacteria-based fertilization system. If you don't have fish, any organic ammonia source can work. In a TEOTWAWKI situation, the ammonia contained in human urine can work just as well as what the fish produce, and while waiting for my fish to arrive, I actually used this technique to jump start the bacteria in the system. The result was that the water clarity improved once the bacteria were given enough ammonia to thrive. Another option if you don't have fish is to use the ammonia and nitrogen found in a "manure tea", which is made by placing horse manure in a burlap bag and immersing it in the water tank for short periods of time.

Dissolved oxygen in the water is another important topic. Using an air pump to diffuse oxygen through airstones in the fish tank improves water quality by helping the aerobic bacteria to grow and the fish to be active and healthy. Without an air pump, you cannot raise enough fish to power the nitrogen needs of the plants. I purchased a 65 liter/minute Eco Plus Commercial Air Pump from AquaCave for $79.95. This pulls 35 watts on 110 AC, and is quite sufficient, as it easily powers four 12 inch airstones in the tank, plus 4 48" flexible air curtain diffusers I buried under the gravel in the grow-beds to help aerate the bacteria there. This is a floating piston commercial type of air pump, as the standard diaphragm pumps would not have enough power or longevity. For a backup system when the power goes out, I bought a 25 watt 12 volt DC air compressor from AquaCave that runs directly from a 125 amp-hour marine battery, which gives over 2 days of run time. To kick in the DC compressor when the 110 AC power goes out, we used a small plug-in DC transformer to hold open a relay, both of which we ordered from Jameco. When the 110 power goes out, the transformer loses current, and the relay closes which completes the circuit for the DC compressor to draw power from the battery. For a large Aquaponic system with over 100 fish, you have to have redundant air systems, for if the fish go for more than four hours without air they will asphyxiate.

In calculating our total power consumption for running the Aquaponic system using solar panels, the two 330 gallon per hour water pumps for the grow-beds draw 13 watts each, but run only 15 minutes each hour, for an average hourly usage of 6.5 watts. Adding the 25 watt DC air compressor gives a very low total power consumption rate of 31.5 watts. Solar panels and a few marine batteries can easily power this system if you are permanently off grid, and I hope to do this soon.

But to be truly off-grid with Aquaponics involves more than just using solar panels, as you need to create your own fish food as input to the system. Right now, I am using some water containers to grow Duckweed (which is an aquatic plant with high protein that the fish love), but mainly rely on Purina catfish food to feed the fish. To close the loop that would make me independent, I will be building a compost pod that harvests Black Soldier Fly Larvae, along with giving the fish the earthworms from the compost pile. Another protein source I am using is a small electric light about 4 inches over the fish tank with a timer that turns on at night. The bugs fly in and bounce against the light and into the fish tank, where the bluegill snap them up. Now that's a good bug lamp!

The output of produce from the Aquaponic setup is phenomenal. The cucumbers, tomatoes and basil are growing about 3 times faster than in my container garden, and 5-6 times faster than using traditional soil techniques. For more scientific proof on the superiority of Aquaponic gardening, a Canadian research group has written a paper that indicates how Aquaponics outperforms hydroponics. Will Allen of Growing Power has a great video that shows how he grows 1 million pounds of food on 3 acres using Aquaponics. The tremendous production potential of Aquaponics over traditional gardening techniques should make anyone that has a greenhouse investigate Aquaponics.

My next step for the Aquaponic project has been to develop a Nutrient Film Technique (NFT) setup, which consists of running the fish effluent through 20' long sections of vinyl gutters, which feeds the plants that are mounted with their roots in the gutters. Thin plywood is mounted on top of the gutters, with a 2" hole drilled every 6 to 8 inches. Inside the holes I put nylon netting that holds some pea gravel to provide support for the plant roots in the nutrient-rich fish water. The top of the plants grow on top of the plywood. The gutters have a 40:1 slope (6" over 20'), and a small pump puts water into the high end, with the water transversing the gutters and draining back into the fish tank. This is nearly identical to a standard hydroponic setup, except I am using renewable fish effluent from the fish tank instead of purchasing standard hydroponic chemicals to feed the plants.

YouTube is an excellent video resource for understanding the various Aquaponic systems. A quick search on YouTube for "Aquaponics" will bring up many videos. Be sure to find the videos by Will Allen at Growing Power (an aquaponic farm in downtown Milwaukee ), or by Nelson and Pade who did much of the original Aquaponic research, or any videos by "Backyard Aquaponics" which is located in Western Australia. Aquaponics is very big in Australia as it is a good solution for gardening in a dry climate. One of the best technical articles online to understand the technology of Aquaponics is "Optimization of Backyard Aquaponic Systems." Any articles written by Dr. James Rakocy of the University of the Virgin Islands would provide another expert source for Aquaponics. Wikipedia also has a good article that gives an excellent overview of Aquaponics, and the picture in Wikipedia of the "small portable Aquaponic system" (which came from Growing Power) is the model I used for my system. I just kept looking at this picture, and it finally dawned on me how simple this is. For more technical advice, the book "Aquaponic Food Production" by Nelson and Pade will teach you everything you need to know.

Most preppers live, or hope to live, as far away from the city as possible. But the problem with rural life is the lack of a steady income. An Aquaponic greenhouse can potentially earn enough to make rural living possible, as long as you can occasionally get to a market to sell your produce. Aquaponics is the only type of hydroponic vegetables that can be certified 100% organic, as all other types of hydroponic vegetables use inorganic chemicals for their nutrients. Premium organically raised vegetables will command much higher prices at restaurants and stores that cater to health conscious buyers. But Aquaponics gives you something that no other organic producer can create, and that is, organic produce with roots that have never touched any soil. You can sell lettuce and other vegetables with the roots attached, as no dirt will have ever been on your roots. By leaving the roots attached and not injuring the plant, the "living lettuce" and other vegetables you sell will keep much longer and your profit will be greater.

The one final thing I have to say about Aquaponics is that it gives any prepper something even better than a nearly endless supply of food, and that is, a large quantity of water. If everything else fails and I end up eating all my fish and produce, I still have 960 gallons of water that I can filter and use. In fact, if I extract the water as it comes out of the gravel-filled grow beds, it already has a good amount of filtration, and is probably healthier to drink than the chlorinated and fluoride filled water that comes out of a city tap. Every prepper needs a large amount of stored water, and this is a great way to do it.

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