By Paul Fischer
“Aquaponics” is a combination of “aquaculture,” or the farming of fish, and “hydroponics,” which refers to growing plants in water. The crops help each other; the plants remove waste from the water, while fish fertilize the plants. After some research, I decided to try this for myself.
I used an oval livestock trough for my fish tank, and a lined wooden tray filled with gravel on top to hold the plants. A very small fountain pump on a timer periodically floods the tray with water from the fish tank, keeping the plants wet and filtering the water through the gravel medium. The filtered water then returns by gravity back down into the fish tank.
For fish, I decided to use tilapia. These hardy, tropical fish are available locally and they are good to eat. For the plants, I used a variety of potted plants resting on the gravel medium. The plants’ roots pull nutrients and water from the gravel. You typically have to feed the fish occasionally, but tilapia can also survive by eating aquatic plants in their tank (I use anacharis) and by eating guppies kept in the tank for mosquito control.
The whole setup took a little bit of tinkering, but eventually I got the hang of it and had some pretty good results. I had to experiment with different crop and tank plants and how much food to feed the fish. In about a year, the tilapia got about the size of my hand, and we got a meal or two out of them.
The bigger reward comes from thriving vegetable crop. I found it a little easier to tend my aquaponics garden than a conventional garden. The plants grow at tabletop height and there is a lot less upkeep in the form of weeding and watering. Also, feral cats and chickens don’t bother my aquaponics, whereas they scratch up my conventional garden terribly. I had some success with salad greens, tomatoes and Swiss chard. I haven’t had a chance yet, but I would like to try growing watercress and other edible aquatics.
Make sure that if you attempt an aquaponic system, that you eliminate the hazard of drowning or electrocution for both humans and pets. Those types of incidents would make the entire project a disaster.
I would say that backyard aquaponics is a worthwhile activity, but it doesn’t replace conventional gardening in the ground. I particularly enjoy raising the fish. On my newest system, I am raising tuxedo platies, which are an ornamental aquarium fish.
If you are considering aquaponics, I recommend reading articles and watching videos on the Internet. I found them a big help. Also, some people are already doing aquaculture and aquaponics on Molokai. Ask around, as they are a great source for advice as well as fish and plants.