keith_r

In writing this I knew that these kinds of questions and challenges were going to come up. That is why I took care in my wording and am saying that this is not cast in stone. I have to look at my post for in my mind I am several posts ahead of what is published. I find it gets a little confusing for me to keep track of what you have read.

The stocking densities are like everything else, a combination of others and my own experience. As our fish grew out, I watched carefully the system chemistry. As we planted different plants and watched them grow and some flower, I noticed the chemistry change. Later, as the fish got bigger and we fed them more food and a second planting happened, I noticed the chemistry changing as it did with the first planting. I also noticed that it was becoming more difficult to keep the system in the acceptable range and balanced. That was when I focused on increasing the DO in the water. Over time and a number of changes to the system it has come back into balance and stayed there. I keep a log of every change in the system and record all the numbers in it. This includes the usual water chemistry as well as the amount of food given the fish (automatic fish feeders with precise metering of food), tank temperatures, DO in each tank. pH, and TDS, as well as any fish death or tank change.

Once the fish reached one pound per three gallons of fish tank water, I again noticed a sensitivity in the balance. More DO was added and it again settled back down. At this point there is not much, short of adding pure oxygen to the water, that I can do to keep the system stable if I increase the poundage of fish; for the DO is currently between 6 and 7 ppm. So, I have concluded, as have others, that the one pound per three gallons of water, given the volume of grow beds I currently have in the system, is a maximum. This is where I came up with the number of 3.3 pounds of fish per gallon of grow bed capacity. The reason for the 3.3 pounds is because we only have five grow beds (due to space limitations) when ideally we should have six, so I have calculated the ratio to show our actual grow bed to fish density ratio. If I increase the number of grow beds (which will require a redesign of the system) then it should be possible to up the number of fish. But this will compromise the idea behind this series of posts, which is to tell how to build a simple Aquaponics system that will produce food without pushing the limits of Aquaponics design. I want people who are new to Aquaponics and are building and operating their first system to be successful.

By the way, we have some fry and fingerlings in one of our three connected (water exchange only, no fish exchange) tanks. As they grow out I will be keeping an eye on the chemistry as always and it will again challenge they system. It may be time then to harvest some fish, as we have yet to do that.

Oliver