In my opinion you will see the most interesting behaviours when you have a group, six or more. Obviously they need an appropriately large tank.
Typical tankmates are
- tetras selected from the chunkier species, such as cardinals and rummynoses, which won't be tasty morsels for the angels
- small cichlids like rams, which will occupy the lower part of the tank
- corys which will occupy the surface of the substrate
- hatchetfish, if you have a covered tank, as they are notorious jumpers.