Kuhli loaches, clown loaches, and rainbow loaches come to mind. The kuhli loaches are small peaceful loaches that do best in group,. Clown loaches can get big but take years to do so, schooling, and peaceful. The rainbow loach in my experience can get a bit aggressive when there are to many bottom dwellers that they encroach on his territory but other then that they are a nice addition. They get up to 6 inches and do best if they’re the only rainbow loach in the tank unless it’s a large tank.
Are you looking for suggestions for other fish besides loaches? I can recommend several other fish that I have experience with that I believe will do well in your tank and I can even help you with plants.