I ascribe to the idea that the more water changes the better. I try and do 50% every 2-3 days. But i unfortunately an overstocked at the moment. Trying to thin my herd, but I'm swamped with babies atm. The butterfly would be cool with the bichirs, what if you did that and tried to find one of the nicer crayfish? Google cherax sp. And you'll see some really nice ones