A 90 gal footprint can only house one full grown BB or Frontosa, with a few small tankmates, but no way have room for two 14' fish together. Despite known to be mild temper, my 12" Front is a silent killer wiping out half a dozen of my 7 to 8" haps and GT in a sudden turn to aggression. He ended up living alone in a 75 gal with a bunch of tiny Tang that can hide in the rocks. He never bothered tiny fish anyway. I have no experience with Black Belt, and assumed BB has the same temperament as Syns, so I could be wrong. But looking at the video, the BB were kept in breeding pair, and that could be the problem. My strategy of a mixed tank is to keep big fish singly, never in pairs, but it's OK to keep a bunch of small fish in pairs.

