First off, the zebra danios are pointless. They will be eaten and can cause malawi bloat in mbuna due to the higher protein content (not in the natural diet for mbuna typically). Either fish are used to bring shy fish out of hiding. The concept is that the shy fish sees schoolers (aka prey fish for most predators) out in the open, so it must be safe. Dithers aren't used to curb aggression. Target fish can be used for that, to keep one fish from beating another fish. These are used more so in more aggressive tanks or breeding tanks to keep the male/female from beating it's mate.
Ok next, Saluosi may be a dwarf species, but their conspecific aggression is typically pretty high. I don't hear of them working out well long term in a 3' tank very often, I believe AndrewMcfadden on here is one of the few I've heard from that have had it work. So I would look more into that if I were you. Playing with mbuna in a tight space is like playing with fire typically. Sometimes you can contain the aggression/territorialism, other times you'll end up with a single individual.
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