03 May 2011

Aquaponic Adventure

Have you ever heard of aquaponics? It's a food-growing system that combines hydroponics with aquaculture (fish farming). The problems with hydroponics and aquaculture are that you have to constantly add nutrients to a hydroponic system, and remove waste products from aquaculture systems. Aquaponics, however, is a closed system: the waste from the fish provides nutrients to the plants, and the plants filter the water to send back to the fish. You do have to make slight pH adjustments and top up the water, but that is pretty much all the maintenance that needs to be done once the system is up and running.

We've started building a small aquaponic set-up in our garage. We mounted the frames from which we'll hang the grow lights this morning. A couple of weeks ago, our re-purposed food-grade barrels arrived, and we cut the top off the barrel that will hold the fish, and cut the other barrel in half to make two grow beds. This is a common first aquaponic set-up, and when we have a frame built for the barrels it will look something like this. For fish, we will start with inexpensive goldfish. That way, we won't be heartbroken if things go wrong and the fish die. Once we have things going, we will introduce an edible fish like tilapia or another variety of perch. These fish are omnivorous, so they'll eat trimmings from the plants as well as fish food, and they are tolerant of the water temperatures we'll be able to achieve without a heater or very deep water (unlike trout, that require colder water). They also grow to eating size in about six months!

But when we get the plumbing together, we'll just have goldfish. They'll feed the veggies well enough. There are two ways to grow the veggies--on floating rafts, which requires the solids to be filtered out of the water, or in grow media like gravel or clay balls. We'll be using grow media, so we don't need a filter.

There are all kinds of extensions to the system that people have posited, if you want a more comprehensive food-growing operation. One that was proposed in a recent, interesting TED talk by Charlie Price of Aquaponics UK posited a system that included chickens and two sets of worms or grubs. One set of worms is fed to the chickens. Chicken waste is fed to the second set of worms. The second set of worms are fed to the fish. Fish waste feeds the plants, and waste from the plants (old plants that are no longer fruiting) are fed to the first set of worms. So now you get eggs and meat as well as fish, fruits, and vegetables. If you could work in a goat or two you'd have a farm and all food groups represented.

The main advantage of aquaponics over traditional vegetable gardens is growth rate, fruit production, and in an indoor system, protection from insects. We planted our lettuce, tomatoes, basil, carrots, beets, chives and parsley outside weeks ago. They are still tiny little sprouts, and many of them died because the weather has been unfavorable (high winds and alternating heat with torrential rains). We also have an infestation of strange little white ant-like insects who are eating the peat pellets that we started the seeds in, and damaging the seedlings' roots in the process. This won't be a problem in the aquaponics system. We'll probably have to deal with fruit flies, but that's easy to handle. Aquaponically grown plants grow faster than traditionally farmed produce, as well. The grow lights help with that. Check out the pace of growth in this aquaponics system: comparison pictures. The tomato plants that I started indoors in February and transplanted into pots rather than into the outdoor beds have taken twice as long to get that big.

So, here we go! Fresh veggies in another couple of months.

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