I have a 29 Biocube and have 12 crabs, 12 snails, a fire shrimp, a pistol shrimp, 2 clown fish and a six line wrasse. I also have a torch coral, frogspawn, asst. zoa's and ric's. A colt coral, star poly's and a kenya tree. The 12 crabs and 12 snails have done a remarkable job of cleaning up.