Aquaponics - a food production system that combines conventional aquaculture (raising aquatic animals such as snails, fish, or prawns in tanks) with hydroponics (cultivating plants without soil) in a symbiotic environment. In normal aquaculture, excretions from the animals being raised can accumulate in the water, increasing toxicity. In an aquaponic system, water from the aquaculture system is fed to a hydroponic system where the excretions are broken down by nitrogen-fixing bacteria into nitrates, which are utilized by the plants as nutrients. The water is then recirculated back to the aquaculture system.
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It was early in 2013 when I first learned of Aquaponics, stumbling upon the topic while browsing the internet. Intrigued, I thought I would give it a whirl, since the concept seemed to fit well with my family's goals to be less-dependent on the grocery store for our food, and to better control the quality and freshness of the food we eat.
In early May I purchased about 100 tilapia fry (baby fish) from a farmer near St. Louis for $20, and thus the adventure began. Initially I placed the fish in a small 10-gallon aquarium. While they grew, I prepared for the next phase of the experiment. I built a 4' x 8' grow-bed out of 2 x 12's and plywood, locating it outside on an existing unused concrete slab. It was filled with about 30 cubic feet of pea gravel purchased from a local quarry for $10. An 8-foot diameter x 18" high kiddie pool from Wal-Mart ($15) would hold the water, about 500 gallons of it. A small 45-watt 550 gph pond pump from Amazon for $35, a few pieces of PVC pipe and fittings, and everything was ready.
The weather had not quite warmed enough to safely move the fish outside, so I used the time to begin "cycling" the system by introducing a small quantity of ammonia into the pool water daily. This simulated the presence of fish and provided food for the beneficial bacteria that would eventually colonize the gravel bed and later convert the actual fish waste (which would otherwise build up to toxic levels and eventually kill the fish) into relatively harmless nitrates. It took about 2-3 weeks for the beneficial bacteria to set up shop in sufficient numbers. The seedlings I began planting in the system consumed the nitrates they produced. Once the water chemistry was balanced and steady, it was ready for the fish.
The tilapia moved to their new pool-home in late May. It was none too soon because they had out-grown their 10-gallon tank weeks prior. The fingerlings continued to grow quickly over the summer months, as did the vegetables in the grow-bed. In order to determine which kinds of plants were best suited to growing in this system, I planted a wide range of normal things you would find in a typical garden: cherry tomato, bell pepper, string beans, eggplant, zucchini, and various lettuces and chard. I even had a corn stalk in there for a while until it blew over one day in a thunderstorm. I replanted it in the soil garden and it survived. Everything in the grow-bed did very well, but I came to the conclusion that any plant needing trellising or staking would be easier to manage if growing in dirt, or at least at ground level. Besides, my wife and I eat lots of salad greens, so why not stick to that for the grow-bed?
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| Click on the pictures for full-sized versions. This was how last year's grow-bed looked by mid-summer. The 100' coil of black irrigation tubing in the foreground is a makeshift solar heater to warm the pool water when needed. About half the output from the pump is circulated through it on sunny days. I am currently using a garden hose for the same purpose. |
Eventually autumn came and as the temperature dropped, it became evident that the fish had not grown large enough in five months to provide decent-sized filets. The decision was made to keep about half of them over the winter in aquariums, inside the house. The other half became dog food (our three canines are on a raw meat diet). I snagged two larger aquariums on craigslist, a 55-gallon and a 30-gallon, with pumps, heaters, and various accessories, for about $100. As it turned out, that was not enough space for fifty 6-inch long fish, so I temporarily re-purposed two large plastic storage bins as auxiliary water tanks. This was still not enough room, but would have to do for awhile. I needed to change the water in all four tanks about twice a week all winter long, even while feeding the fish a subsistence quantity of food. What a bother! It was clear I needed a new plan.
In January I began enclosing a corner of my detached 3-car garage. A 10' x 10' room gradually took shape. Lumber, insulation, drywall, and plywood purchased from Home Depot for the project came to about $400. I already had most of the electrical and plumbing parts on hand, including the proverbial (used) kitchen sink. To house the fish, I bought a quantity of used, food-grade, 275-gallon IBC tanks for $60 each. I kept two of them and re-sold the rest at a small profit, so mine ended up costing a mere $15 each. Gotta love craigslist ! A small $15 space heater from Wal-Mart had no problem maintaining that little room at 80-degrees. I didn't even notice a bump in my electric bill. A rusty old 4-bulb fluorescent light fixture that the previous homeowner left behind in the barn as trash was cleaned up, re-painted, and now provides sufficient light for the interior grow-bed plants.
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| I am about to add a second grow-bed to the left of the one in the picture. Also, a second IBC tank resides under the test kit in the picture and is currently empty, but will be put into service this winter. |
I moved the fish out to their new home in February of 2014. The grow-bed I built for that small room in the garage was only 2' x 4' and way too small for the amount of waste the fish generated. As soon as the weather got warm enough in mid-May, I moved half of the fish (about 25) back out to the pool and replanted the outside grow-bed with lettuce, spinach, and chard. The inside grow-bed was STILL too small for the remaining 25 adult fish, so until I get around to building another bed, I have to use an improvised filter system to catch most of the solids before the water enters the grow-bed. The heart of this filtering system is a used 55-gallon plastic barrel bought for $10. A valve in the bottom of the barrel enables me to drain the solids off periodically. The solids are used as fertilizer in the soil garden, so nothing is wasted.
The plants in this interior grow-bed are thriving. After some experimentation to determine which plants would do best growing under standard fluorescent lights, I settled on "swiss chard / perpetual spinach" from Baker Creek Heirloom Seed Co. This variety lives up to it's name... we have been clipping leaves since April and the plants just keep producing more and more.
Sometime around mid-July, I noticed a few baby fish had gotten caught in the filter floss. Upon closer inspection, I discovered there were hundreds of fry swimming around with the adults in the pool. My fish were finally breeding! I quickly got the three previously mentioned aquariums up and running again, and transferred several hundred fry to these tanks. I built large filters out of used plastic buckets and 4" PVC pipe to handle the waste. These fish are growing fast and will become next year's crop.
Also, in anticipation of needing more space for the new batch of fish as they grow, I have purchased two additional 35-gallon aquariums off craigslist for $30 apiece. Each one of these is sub-divided into three 12-gallon spaces, each partition with its own "through-the-wall" plumbing. These six units will enable me to segregate the fish according to size until they reach about 3"-4" long, at which point they will be transferred into the IBC tanks.
More space is needed to accommodate all these aquariums and to provide for future expansion. I decided to enlarge the "fish room" inside the garage by enclosing an additional 6' x 10' of floor area. The plan is already in the works and I should have the material to begin construction by October 1st. This 60% expansion will essentially become "the nursery", with various aquariums and their attendant filtration systems on dedicated shelves. That will allow me to re-claim the counter space currently being occupied by the fry tanks. I also want to try my hand at vermiculture. From what I've read, adding worms to aquaponic grow-beds will enhance the efficiency of the system. We shall see.
It is currently late-September (2014) as I am writing this blog entry. The 17-month-old adult fish are about a foot long, on average, and now ready for harvest. This must happen before the end of the month, since local overnight temps have been dropping into the 40's pretty regularly. By circulating some of the pool water through about 200' of garden hose on sunny days and keeping a solar blanket over the pool during the night, I have been able to keep the water temperature above the danger zone. Tilapia are tropical fish and are stressed at water temps below 60, and cannot survive at all below ~ 50 degrees.
The netting over the pool prevents hawks from grabbing an easy meal. I haven't lost a single fish to predation yet.
it's what's for dinner! (soon)
Once the freezer is stocked with filets, and as the new generation of tilapia grow into fingerlings, they will eventually be moved into the empty IBC tanks. Of course, much smaller fish generate much less waste, so hopefully the existing grow-bed, combined with a second one I intend to build shortly, will provide ample filtering through this coming winter. Additionally (and conveniently), one of the exterior walls of this "fish room" faces due-south, so my plan is to build a 16'-long x 24" wide grow-bed outside along the wall and plumb the IBC fish water to and from it through the wall. This will more than quadruple the grow-bed volume I currently have for the IBC tanks, and will enable me to grow a wider variety of plants next season. It should also eliminate the need for additional mechanical filtering of the water.
This is what the outside grow-bed currently looks like. in the foreground is "May Queen" butterhead lettuce, almost ready for picking. Behind that is "Parris Island" romaine-type lettuce, (some heads already consumed). And lastly in the background is more Swiss Chard - Perpetual Spinach. All these varieties have grown well without the need for supplements or any special care whatsoever.
There is also room for more grow-bed space on the concrete slab. The plan is to build a 16' x 4' bed adjacent to the existing one and thereby triple the space for plants and pool-water filtering. Hopefully this will be done in time for next spring.
I will post a new entry here in about a month when the new "aquarium addition" is finished.
