That MBU has been with way smaller fish and has not winked at a single living fish. I recently removed some of the Tropheus that was with him and soon will be moving out the Petrochromis so it will just be the ERH and the MBU. I have 4 baby bichirs in the tank that lay beneath him with no problems and even housed a mass of tetras/barbs in this tank with no problems. Oh... there was a betta in the tank before the ERH were put in as well.