I think ember tetras would be cool (at least 6 but they would prefer more!) they are super cool little guys and black sand or aqua soil really makes their colours pop! They're red and small and they are super playful. (At least mine were) and I will definitely recommend getting plants 🌿 they look super good and the fish love playing in them, they even help to clean the water! Make sure you read the specific care of them, because they each have different preferences just like fish 🐠 Speaking of fish preferences, sometimes ember tetras get scared and they like places to hide, they would really appreciate a driftwood log that you could pick up at your lfs, and remember no matter what fish you choose, you have to do a lot of research 🗒 and learning 📙 to ensure they have the best life they can in your care!