It's a barb relative, by the way. The shark marketing name has sold a lot of them, and that's probably not a good thing. They are very antisocial, living in good sized territories and not sharing space except to spawn. The circling fish are probably hoping to kill each other. They've probably come of age, and decided their tankmates are really annoying. They really are a fish that should be one per tank. They have a way of regulating that themselves, via murder.
They are bred via hormone injections on Asian farms, so dealing with fry won't be an issue. I doubt you'll be writing about how to hormone load hypodermic needles for them! I knew a creepy Russian guy who used to hormone inject Discus to breed them, and he showed me once. Not good, in my books.
They come from fast moving rivers, so they like a good current. That may be the only way to diminish their aggression, as river fish in slowing moving tanks seem to direct the energy they don't need for swimming into fighting.
