Well I want a one mid swimmer to top fish with my polys.I'm not the person to ask on cichlids, not a fan of them haha. There are plenty of smaller species that will work in a 75, but as for aggression or the possibility of them becoming a meal themselves, I couldn't tell ya. My instincts tell me to suggest convicts, they are generally fast enough to avoid being a meal, but I would then worry about them turning out to be aggressive towards the polys. Are you dead set on having cichlids with them? I can make multiple suggestions of other fish that work well.