I have a 14 gallon biocube that I modded to include a sump, so it probably has closer to 20 gallons in it. It's easier to keep than my 140, I think, because I don't expect as much from it. I don't put much sps in it. I know that it is healthiest with only 3 fish in it. With my nano, I maintain, I do not chase numbers. It works well with 2 clowns and a yellow watchman, a pom pom crab, a hermit crab, a tiger conch, a couple of margarita snails, and for coral I have a bta, a large trumpet and toadstool, a couple of acans, and some zoas. I don't dose. I think water changes replenish what's taken up. I will not add anything that will throw this balance off.