Although Aulonocara / Peacocks don't have the plant eating reputation of Mbunas, it's been my experience that Peacocks will eventually chew on aquarium plants. I tried Anubias & Java fern. The plants lasted for a couple of months, but the constant gnawing ended up ruining them.
A 75 gal. Tank could easily house seven or eight adult Peacocks. IMO instead of plants, decorate with limestone rocks.