Stupid, ugly fish, with no redeeming characteristics as an adult. Don't be fooled by the cute little ball of juvies schooling in dealers' tanks. They get big, solitary, drab, and they hide. And to answer your question a 90 is big enough for 2, as long as you don't intend on adding much else in the way of bioload. But to put that effort and expense into a couple of juvies and have them turn into the turds they inevitably become makes little sense to me. If it makes sense to you, knock yourself out, or better yet seek professional help!