FoodMachine & Water Quality

Location: Kona, HI and Tacoma, WA | Published: 20 January 2011

Water is the life-blood of the FoodMachine. The water facilitates the symbiotic nature of the relationship between the fish and plants. The water carries the nutrients to the plants from the fish and the water, after being cleaned by the plants, obviously provides the home for the fish. One of the keys to a successful FoodMachine is good water quality management.

There are a couple of key indicators of water quality that need to be watched. The first is pH. We have found that neutral pH, 7, is optimal for both the plants we are growing and the fish. Having too high or too low of a pH level will kill fish, which is obviously not a good thing! There are pH buffers that can be used to keep the pH around the neutral level.

Ammonia is another key ingredient to water quality. Fish waste is the major source of ammonia in the system. Especially when fish are added to the system initially, there can be a spike in the ammonia level while the necessary bacteria are getting established in the system. The right bacteria are key to the success of the FoodMachine. The bacteria convert the ammonia to nitrites and the nitrites to nitrates, which are the food for the plants. It takes time for these bacteria to get established, but once they do, the system should balance out to and remain at the correct levels.

Dissolved oxygen (DO) is the other main thing that needs to be tested in the water. Tilapia, which are the fish we use in the FoodMachine, need a minimum level of 4 parts per million (ppm) in order to survive. The amount of time it takes for the level of DO to drop too low depends on the density to which the fish are stocked. For example, if you have one person in an air-tight room, the oxygen level in the room will remain high enough for someone to survive for quite a while. However, if there were fifty people in that same size room, the oxygen would run out much faster. The same is true with tilapia. The more fish are in a tank, the faster the DO is diminished. If the DO can be raised to a higher level, however, a greater number of fish can be stocked in that same space.

As you can see, there are a number of things that need to be looked at when considering water quality. As has been mentioned, once a FoodMachine gets established there are generally no additions that need to be made to a system. But, during the first weeks water quality is something which needs focused attention.