The Goodeids seem interesting, however, I think they will be a bit much for me to start with. In particular it looks like I will not be able to have a big enough tank to have a sufficient number to allow for proper behavior and breeding. I will definitely keep them in mind for the future though. They seem like very interesting fish. Particularly the life history of early maturation, long(ish) lives, large fry and many clutches. Usually, early maturation is associated with shorter lives, fewer clutches and smaller fry, but larger number of young per clutch. I will have to look into what pressures they have that have led
to the less common set of traits.
Any other ideas for fish that are relatively easy to care for, can live in a small (15 gallon column) tank, and show interesting behaviors?