Chili raboras, dwarf spotted rasboras, emerald rasbora, ember tetra, celestial pearl danio are a few that pop to mind.
If the tank is big enough, there are a few more options too. If the tank is 10g, there are also clown killifish, norman's lampeye killifish, Endler's livebearers, sparkling gouramis, ruby tetras, jellybean tetras, and green neons.