I finally finish up reactivating my aquarium, by purchasing some fish and miscellanea.
Three Black Molly (one male), ten neon tetra and one ampullaria (a snail).
I think that's fairly balanced for my aquarium size (50 liters). They're all south american and... the Black Mollies eat primarily from the surface, the tetra down in the water (if you look at how their respective mouths are placed).
And lemme tell ya 'bout the ampullaria! Dat's one busy li'l critter! Nothing sluggish or "at a snail's pace" about that one. It zooms across the glass and the gravel, grazing and nibbling on algae. It's the only lifeform in my aquarium that works for a living. And one fantastic thing: I had saved some plants in a large glass jar to use when I restocked the aquarium and they had a coating of algae. The ampullaria crawled over those and it nibbled away the algae and left the plants themselves untouched. Earlier I've had to remove the plants and scrub them with an old toothbrush to get rid of it. Amazing, well worth its money.
All in all, hopefully a viable biotope. Maybe the mollies will breed. And the ampullaria is a snail, and they're hermaphrodites, so who knows?