Notes from Windward: #69


Prepping the Aquaponics

Jon brings the first system online

     Windward has two aquaponics systems already built. Inside the greenhouse we call Vermidise is an aquaponics system called barrel-ponics. It basically involves cutting open a couple large plastic barrels, a small water pump, and PCB pipes to cycle water from a fish tank to several soil-less growing beds. The water not used by the plants then drains back to the fish tank, creating a closed loop system. When I first arrived at Windward the barrel-ponics system was shut down for the winter. My first project was get the barrel-ponics system up and running. I spent the first day cleaning out all the barrels, gravel, and pipes. Then, I tested and cleaned out the water pump.

the barrelponics system

     All that was left was the 200 gallon fish tank. The water had been sitting all winter long. I assumed the goldfish that had lived in it last summer would surely have starved to death and/or died of lack of oxygen, since the water had not been changed. However, to my surprise, as I lowered the water level in the fish tank I began to see little orange dots in the water. The fish tank is about one and a half feet deep. I lowered the tank to about 4 inches of water and counted 11 live goldfish!

our over-wintered gold fish

     The living goldfish are a very good sign that the water cycle in the fish tank is still healthy. I think the fish slowed down their activity and eating during the cold winter when the water froze. I added about 10 more little goldfish to the original 11 in the tank. I also added a lot of fresh water to the tank and let the new and old water mix just as the added little goldfish were starting to mingle with the larger original 11 goldfish. The plan is to eventually to be growing Tilapia. However, since goldfish only cost 30 cents each, it is much cheaper to experiment with the little ones before switching to larger Tilapia.


Goldfish are a fancy type of carp, a fish that is so central to aquaculture in China that they've developed three basic types: surface feeding, middle feeding and bottom feeding. While raising tilapia is our goal, it's good to know that we can over-winter carp since while they're not as desirable a fish, carp are another way to convert grass and earthworms into edible protein. Gefilte fish is a traditional food made from carp.


     Now that I have a good number of goldfish in the tank, I have started to plant lettuce in the grow beds. I hooked the water pump to a timer so that it goes on for a couple minutes every four hours. Once, the system is running, the only work that is involved is feeding the fish. However, the barrel-ponics system had several leaks that took me two attempts, using silicone caulk, to stop. The great thing about aquaponics is that it is an incredibly efficient close loop system. Fish waste fertilises the plants, while the plants filter the water for the fish. Yet, this interdependence also means that one small leak can potentially slow down or halt the entire system!

Notes From Windward - Index - Vol. 69