As the title states I've got a 55 to setup in addition to my high tech 40 breeder... not necessarily looking to donplanted but here are some thoughts.
I've kept aggressive south American cichlids, angels, raaimbows, no saltwater.....
A. Fowlr saltwater Moray and predator tank
B. Bare bottom discus growout tank of 10 discus or so, to eventu ally gon into an150
C. Exodon species tank, they're like mini piranhas.
E. Mudskipper tank
Open to other ideas but post your thoughts