I have a 20L and I go skimmerless: 1 clown, 1 brittle star, 1 turbo snail, 2 hermit crabs, 1 rock crab that came on rock,A gold coral banded shrimp, 1 hairy arrow crab,1 cleaner shrimp, and a bubble tip anemome and I have had no trouble, :wink: good luck