my maingano have breaks in some of there lines and they look just like johannii, the only reason i know they are maingano is because they were all blue and its very unlikely that it would be a male only tank as they were all fry. its pretty much impossible to tell the two apart other then when they are young with fry, the johannii should have a mixed colored tank (females being a different color i believe orange or yellow?) and males being blue, if the tank is all blue like mine it is maingano, or you could vent and if it female then you would know it is maingano if its male then it could be either. sorry for the long post.