Are you referring to the 1 fish per 10 gallon rule Hannah? I know im not as experienced as you guys but to me it looks more of a territory issue for happy living. My clowns never leave my torch now, my goby lives in a cave 3/4 of his life. that leaves quite a bit of open space. I housed my friends lawnmower blenny for a few weeks for him while he was re setting up. He was fairly large too. They all did fine togeather, never got in eachothers way, no spats. I really have no plans on adding any type of fish other than a sand sifter. But if its going to mean getting rid of Goby-won, its not worth it, Thanks for the input Hannah. :)