Given I already have a 55-gallon planted and am working on a 55-gallon reef, I'd want to do something different. Don't really like cichlids. Hrrm...I'm going to say one of these two options.
1. Freshwater paludarium, Orinoco biotope, heavily planted. Include Black Morpho Tetra, Blackwing hatchetfish, Nannostomus anduzei (pencilfish), Otocinclus vittatus, and a pair of Rams. Above the water, have Dendrobates leucomelas (a type of Poison Dart Frog), and a suitably small frog of the Hyla genus.
2. Brackish paludarium with salinity of about 1.005 planted with mangroves. Stock includes group of Indian Mudxkippers, Fiddler Crabs, Red-nosed shrimp, Bumblebee Gobies, and nerites.