From what I understand the Long Nose Yellows are the easiest to keep. Copperbands are the hardest. I seem recall reading Fenner gives them about 30 days tops. I'm thinking of trying a Long Nose in a 50 gallon corner hex as the only fish in the tank. I have been shopping around for a small one, around 2" But I think most Butterflies grow to about 4 or 5 inches as adults. But I think the LNB is cool enough to be the single star in my FOWLER.