I think you can easily do 15 or a few more (overstocking is goodfor these) as long as their the right types. AND you keep water changes up and OVER FILTER Unfortunately the peacocks need more room as they swim more and get 7 inch but could be kept in a 55 for a while. The Johanni get bigger and are nasty and the crabro (bees) get even bigger. If you did some smaller 3.5 to 5 inch more timid guys you'd have better success but hey let it play out and be ready to give some away or move them if need be. Some timid smaller types are yellow labs, rusty cichlids, clown labs, textilus, lots of the cynotilapia afra many kinds of these. Perlmutt, saulosi (my number 1 fave) Polit. Long list but most local stores don't carry them. They'll likely special order for you.