I'd say 3-4 tetras also. Make sure to get little tetras-neons, black neons, cardinals, lemons, or embers (hard to find). Rasboras would work too, I've heard they're a bit more exciting than tetras. Other possible choices: guppies, a dwarf gourami and a pair of african dwarf frogs, or white cloud mountain minnows. Edit: Wow, what happened to the order of replies on this thread?