coldmachineUK
Aquarium Advice FINatic
I had a pretty bad experience with an RTBS recently: I thought he'd get along fine in a tank of eight malawi mbuna cichlids. If anything I was worried about HIM. Anyway, he bullied them so badly I've moved him out. That was in a 36G, so I'd think you'd have problems in a 20G with one.
I'd go with a pair of dwarf cichlids too tbh. They should be peaceful enough to get along, but also have some personality that will keep your tetra school as a school.
Apistogrammas are lovely as someone said, but I think your tank is too small for them (best kept in groups of 10+ is what I've read recently in Practical FishKeeping. Speaking of which, if you're in the UK you should get that mag it can be a godsend sometimes!).
I'd go with a pair of dwarf cichlids too tbh. They should be peaceful enough to get along, but also have some personality that will keep your tetra school as a school.
Apistogrammas are lovely as someone said, but I think your tank is too small for them (best kept in groups of 10+ is what I've read recently in Practical FishKeeping. Speaking of which, if you're in the UK you should get that mag it can be a godsend sometimes!).