Snails are a safe bet. Shrimp are very low bioload, so those are good. For other fish I would agree on cories or platies. I have a 10 gallon with platies and a betta and I love it.
Tanks- 55 gal(in progress)-Common pleco, Angels, lemon and rummynose tetra, blue rams; 29 gal planted- rasboras, corys, otos, clown plec, shrimp; 10 gal- juvenile goldfish; 6 gal planted- betta
Other Pets-Maggie(Tricolor Paint Mare), Lily(Sun Conure), Zoe and Melina(Budgies), Leonardo- Bearded Dragon, Pilot and Phoenix(Golden Retrievers), Beckham(german shepard/akita), Myrtle and Richard(hermit crabs)
A Better Betta Fish Care Video!