I don’t mean to poop on your parade, but I just did a quick search on poly fish and it doesn’t look like where are too many species suited for a 75g tank, if at all really.
The smallest one is listed at 11”, which is great, so you would think, but this fish needs floor space, there’s not a whole lot of floor space in a 75g tank. Then if you put another species in the tank with this poly (if your lucky enough to find one of the “smaller” species in your area) and say you put two fish in and they pair, they will take up floor space with their nesting area leaving less for the poly.
That 11” poly is kind of like a small Oscar fish....would you keep two Oscar fish in a 75g with a couple of other cichlids?
I even think a jewel Cichlid or acara might be too small of a Cichlid to keep with a poly and eventually would be dinner.
If you kept a poly I would limit yourself to one poly and maybe one GT, or one JD.