I am interested in getting one of these; African Butterfly Fish. Is it true they 'need' a 'very' calm surface to dwell under? I have a power canister filter but there's still about 30% of the surface of my tank which has a calm surface. Is that ok? Would adjusting the output downward in the tank help? I have 4 silver dollars and a standard pleco, will that disrupt their living habits considering the current now being put into their level of dwelling?? Thanks for your help!! ~eric