I have read that if you plan to add two of the dwarfs, you should do it at the same time. I see them at the LFS together, so maybe you could try both in your 10 gal. QT at the same time. If they start to fight then put a divider in or maybe that would be an early indicator that they won't be good together. I don't know if I'd put either in first, since it may esablish itself and not allow the other to do so. This is just an opinion, as I haven't had two, only 1 dwarf at a time. HTH