bump up all of those schools to at least 5. then i would suggest a pair of bolivian rams. my black skirt tetras are also very aggressive towards their own kind. they leave other fish alone however, unless the other fish is bullying another fish... in which case they all 6 turn on the bully lol. i would say instead of adding shcools, bump up the numbers to about 8 each. the larger the schools the more spectacular the schools look, and adding a ram or other dwarf cichlid would really bring the tank together. now, i would also say angels could be a good fit, but you shouldn't do them if you do black skirts.