Backyard Aquaponics
A place to discuss aquaponics

I currently have a bit less than a 1:1 ratio of gravel to tank right now. I think my level fluctuates by about 4-6 inches right now at it's most extreme. Two of my grow beds flow into what I had been calling a "sump walk" that I was going to hook to the tank with a float valve but the flow through on all the float valves is way too small to keep up and avoid overflowing the "sump walk". So, that is really just functioning as a flow through tank. The 1 1/2" bit of pipe between the "sump walk" and the fish tank slows the flow a bit and probably buffers the fluctuations some. The other two beds drain directly into the tank.

With a 1:1 ratio, the fluctuations are not too big an issue with many species of fish but if one had the recommended 2:1 Gravel to tank ratio, the need for some way to maintain tank level becomes apparent.

I've heard of people using separate pumps/timers for different beds. I've also heard of people trying to cascade beds. By far the most popular method seems to be sump tanks but to be effective they really need to be plenty large enough.