Rift lake cichlids like Malawi Peacocks much prefer very hard, alkaline water (NOT good for plants) and many of them will chew your plants right down to the stems. I can recommend the 'kribensis' and its relatives, Pelvicachromis sp. They are very active and colorful, don't grow to excessive size and will probably spawn in your aquarium for you. However, lest I paint too rosy a picture, 'kribensis' are cichlids and share (to a lesser degree) that group's general propensity for re-arranging the tank to suit their needs, especially at spawning time. Fortunately, 'kribensis' are cave spawners and won't excavate enormous pits in your landscaped aquarium. Like most cichlids, 'kribensis' can be aggressive, especially the males. With an 85 gallon tank, providing you give the fish a number of caves to work with, you shouldn't have any trouble keeping a number of pairs of this gorgeous fish!