It'll do the job... maybe, but it's not very nice to the fish. If you're lucky the females will get along, but the fact is these cichlids don't like each other, and at best they're forced into a truce in a tank. In the wild they're just as aggressive, but there's plenty of room for them to seperate if they need to. They do grow to 5" too. The hex tanks are tall and have a tiny footprint, the 20 hex may as well be a 10 rectangle tank for space the fish use - they don't make very good cichlid tanks. I wouldn't put more then one of them in less then a 20 long.