I have a 55l with what has become a 2 species tank, not that you would know it as you NEVER see the fish. I have a large group of Cobalt Blues and a large group of Yellow Labs in a rocky tank, the yellows are the Left end Gang and the Blues are the Right side bullies. I did have 6 tiger barbs, big ones, 3 green and 3 orange in there, but they ate the Green ones, they killed off a female P.S. Nicholsi, almost killed the male, ripped apart a red tailed shark, saved him in time, so now they are all alone. So, I have learned they are MEAN, and nothing will be added to the tank, just maintain the balance that is there now. Finally my question, these fish appear to be subterranean, they live UNDER THE ROCKS in caves and tunnels they have created and come out for feeding time or a quick cruise, so my question is, how do I correct this? Or is it just the behavior of this species? Should I remove the rocks and use more of a bare landscape? Should I create a pile of rocks in the centre of the tank instead of along the walls of the tank? Would this correct the disappearing fish phenomenon? Please any and all advice would be welcomed as they just don't look happy. Thankx