thanks jus trying to grow a huge male with a hump headI have four cryptos (relatives of convicts, same size, temperament, etc), in a 70 gallon and there are some aggression problems. You could have at a couple of breeding pairs in a 90 gallon but there may still be territorial disputes. Don't overcrowd it with 40 or even 10, your fish will be immensely unhappy. These fish will grow to be 5 inches long each eventually.
Yeah jus want a big male and a female thats allI love convicts, honestly bro when they start spawning they get really mean! It doesn't take long either, so I wouldn't put too many in a 90.