Dwarves are bottom dwellers and this is where their territory is, so as long as you go with something that won't be a competitor you'll do ok. Many characins, rasbora's, danio's, hatchets.. All will work. Remember that giving them good shoals increases their security and provides too many fish for the Dwarves to target when they're moody or spawning - larger groups of less species is always best. Avoid small, timid, or delicate varieties like neons.
