To start, I want to say that I know my tank is too small for the fish that I have right now. They are all getting along well at present, the Rainbow shark ignores the guarami, even when it strays into it's favorite hiding place, and the shark only ocaissonally, and briefly, harrasses the Flying Fox fish. I will be upgrading within the year to a larger tank, either to a 50+ and then into a 100+ or directly into the 100. I am also working towards replacing the ugly plastic things with real plants, and adding more driftwood. I'd also like to add that I am aware the Rainbow shark will likely become more territorial/aggressive as it gets bigger/older, which is part of why I'll be upgrading to a larger tank.