I have a pink square in my reef tank. It has been in there for about 2 months and is doing great. It took several days for it to warm up to the tank but now seems to be doing great. Very beautiful watching it grasefully swimming around the tank. Does need caves and other large low light areas to hide in. Also gets along great with all my other fish, although he does like to chase and be chased by the sailfin every once in a while. But only a couple quick dashes at each other, nothing to be concerd about. I would suggest doing a good bit of research on what ever species you want. I have been told by several reputable sources they are hardy, require a varity of meaty foods, and would prefer to be kept in schools but not necessary. Hope this helps!