Hooked on Aquaponics

Give a man a fish, he’ll eat for a day. Teach a man to fish these days and he may get mercury poisoning. Teach a man to do aquaponics and he will eat fresh fish and veggies for a damn long time!

I’ve been working on an urban agriculture project in Cincinnati over the past year with three friends. The big idea: to grow fish and vegetables, together. The fish poop provides the nutrients for the plants and the plants filter the water for the fish. It’s a closed loop system, so the water is recirculated over and over again. Welcome to the wonderful world of aquaponics! I’ll walk you through our basic system design.

Our tour starts in the corner of a garage that some generous friends allowed us to use for our fish tank. It was an old dome-lidded water tank that farmers use to haul water out to the pasture. We cut the lid off, patched the leaky spots, and voila! A 600-gallon home for our 300 tilapia. Isn’t that amazing? Tilapia can be grown at about 1/2 pound per gallon of water. Most of them will grow to a pound or so, meaning one fish for every two gallons.

Matt and the 600-gallon tank with biofilter barrel perched (pun intended) above.

Blue tilapia after two months of growth.

From the tank, the water flows out through a pipe, through the back wall of the garage, and into a greenhouse that we built in the back yard. The pipe distributes the water into three vegetable beds. These are basically wood frames that we lined with rubber so that they would hold water. On top of the water-filled beds are sheets of styrofoam insulation that are gridded with holes for our veggies. The vegetables are held in little slotted cups that allow their roots free access to the nutrient-rich water below. Because we aerate the water for our fish, the plant roots are able to thrive in this underwater environment without rotting. In the coming months, we hope to include freshwater prawns beneath the veggies. These creatures like similar water temperatures as tilapia and will act as muck-cleaners for the system, eating algae off the plant roots (which will improve their nutrient uptake) and cleaning up any fish gunk that gets into the growing beds.

Greenhouse with 3 planting beds. Distribution pipe from garage against the far wall.

In the foreground of the above picture, there’s a small experimental wetland that occupies a third of one of our beds. This wetland is multifunctional. It gives us an area to experiment with growing plants in gravel instead of floating rafts. It acts as a supplemental filter because it is full of plants that will remain in place. It looks beautiful. And it allows us to experiment with different crops. In this small 3×5 foot area, we have a papaya tree, passion fruit, irises, canna lilies, turmeric, strawberries, gotu kola, lemongrass, taro root, horsetail, oregano, duckweed, watercress, mint, chives, peace lilies, papyrus, cattails, water hyacinth, water lettuce, water celery, sweet potato, nasturtium, basil and philodendron! Matt and I actually ate the first ripe strawberry three days ago, on the 20th of January!

Mmmm. Strawberries!

After the water passes through the vegetable beds, it collects in a 55-gallon drum and is pumped back into the garage. It passes through a simple filtration system, where bacteria turn the ammonia into nitrates, before landing back in the tank.

So that’s the basic tour. Not so complicated. It’s a really fresh experiment for us and we’ve got a lot of learning to do, but we’re excited about the possibilities of using aquaponic systems to grow healthy food in the urban environment. The beauty is that you don’t have to have soil to make these systems go. You can do it on a contaminated site. You can use old buildings. Abandoned urban industrial sites could be brought back from the brink of decay and turned into lush oases of year-round food production, creating jobs and making healthy foods available to neighborhoods that typically don’t have that “luxury.”

Aquaponics can also be put to tremendous use in other parts of the world, where resources are limited and sunshine is bountiful. From deserts to more lush environments, aquaponics systems can be much more efficient in the tropical and sub-tropical latitudes because there is no need to heat the water. There are possibilities for northern climates with coldwater fish as well, but these fish tend to be less resilient than the tilapia and using cold water is likely to make for a less productive system in general.

Imagine an agricultural renaissance in our urban areas and other typically marginal agricultural lands, our communities bursting to life with elegant food-producing ecosystems on properties that had been left for a slow deterioration! We’ll keep working on things from our end and with any luck, the next aquaponics blog post will be on herb-crusted tilapia filets with boiled taro root and passion fruit marmalade!

Advertisements