As long as the dominos grow up with other fishes the same size as them at first, they may stay relatively well-behaved. If for some reason they ever end up rulers of the midwater and surface, alone, and they've reached considerable size, they'll make it impossible to add other fish of that sort unless you're real fast doing it. I had another of the ilk, a golden, a humbug (she buzzed, loudly, when irritated: you'd think your phone was sounding off) and she was fine until a power-out got my midwater fishes. After that she was a holy terror, about 7" long and bent on world domination.