I,ve got an albino Gibby, a gold nugget and what i believe is a butterfly L168 in my 55 with mostly African Cichlids. Had a Green Phantom, but my Gibby terrorized the poor thing and it didn't make it. The three i have now do really good and don't really seem to bother other fish. But if I was lookinig to stay in a 55 i'd probably go with a Snow Ball or White Spot. They're fairly rugged and don't get very big.