Help! 15 gallon tall?

Hey, I got this tank from a coworker. Measured and it should about 15 gallons. I moved my cardinal tetras into this tank temporarily since they were killing my shrimp in my 10 gallon. I want to get new substrate and make a thoroughly planted scape. Hopefully that can be a permanent home for these guys. Could I add any other fish? I’ve had a hard time figuring out what can live in such a tall tank. I’d like to add a betta but I think it’s too tall for one (about 18in) I’ll probably add snails and maybe amano shrimp but fish suggestions would be appreciated 🙏 thank you!