a crabro will outgrow a 30 gal tank. My female bumblebee was around 5 inches long-she was a big fish. Id get rid of the crabro and get a few dwarf type mbuna-saulosis, a few yellow labs, rusties (not all together of course-the tanks too small)
id get a trio (or one male and 3 females) of yellow labs or rusties-great fish!