Any of the smaller growing peaceful cichlids. For example herotilapia multispinosa (rainbow cichlid), Apistogrammas, Ramirezi, etc. as well as a wide choice of community fish which are compatible with these cichlids. i'd stay away from convicts etc.
I'd rather go with an active fish like rainbow cichlids or one of the small acaras (like Krobia sp.) instead of the shellies which are limited to the bottom of the tank