I really like them and have kept them for a few years, but they get really big. I had them in a 40 breeder for a long time and I think it was a bit too cramped for them. But man, when you get a good sized group of them going, they are mesmerizing: Trout Goodeid School. They are constantly on the move. Every time I walked by the tank, they would suck me in and I was just stand there for a few minutes watching them.
I recently moved my group on to someone else since I needed the space. For a size comparison, the attached image is the last of the group in a 5 gallon bucket. Some of the females are pushing 4 1/2″ to 5″ in length. The babies they produce are near the size of a mid sized guppy.
If you do get some, they are another one of the ‘just add water’ kind of breeders. As long as they don’t get too hot (normal room temperature is fine, no need for heaters), I don’t think there is much you can do to stop them from breeding. Fry can eat the same food as the parents from day one.