cory cats work well, they're bottom dwellers, only thing is they do better in shoals or groups of 5-6. They also need substrate that isn't rough, or it can wear down their barbels, and they don't grow back sadly.
Neon tetras work, but again schooling fish, 5-6 of them. I think some of the plain guppies might work, or platties.
Not sure what else to suggest.