I remember hearing that Hait's were prone to bloat that a change of diet didn't seem to help. It's interesting that separating them seems to have settled all that down. Obviously these guys are much more solitary from an early age that a lot of cichids are, and that being in close proximity to each other is hazardous to their health for more than the normal reasons.
How much does the tank temp drop overnight? I'm curious, as I am doing something similar with my 55 that contains my BGK, Clown Pleco's and Senegal Bichir. It's winter here, so the temps are dropping lower than I expected overnight and not getting as high as most ppl recommend during the day. I've noticed very little detrimental effect of any of the fish, if anything my BGK seems to be thriving.
