I have a 20-gallon long tank with one dwarf gourami, some neon tetras, and a pleco. I've recently been interested in adding a Gardneri Panchax. I was initially concerned about the fish interacting with my gouramis but have found quite a few articles saying they get along ok. I haven't, however, been able to find anything concrete about how many garneri's to get. I don't want to breed them, and I know keeping multiple males will lead to aggression. Can I just keep one of them? If I need more than one, what ratio of males to females should I get? Do I need to sell any of my current fish enable to keep killifish?