| I haven't kept them myself, but I almost got a pair once (turns out the female had died unexpectely before I picked em up). I have heard if it's a good, matched pair you can keep them in a smallish tank (i.e. 15-20 gals) without a problem. Where you run into issues is with poor pairing, where one is likely to kill the other. I doubt you can keep a group together in that size of tank (other than parent/juveniles), but you could probably get a group of fry, allow them to grow and pair, and keep a strong pair and sell the rest. They have really neat breeding behaviour, where juvies will often help rear younger sibs.
Someone else who has firsthand experience might have better advice though! | 
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