I have a 20 gal with 4 wild type mouthbrooding Betta edithae, endemic to Borneo.
It was first set up just to grow put plants, but the Bettas seemed a perfect fit.
I have a 5 gallon with some plants and 2 rosies that for some reason i never got around to feeding to my eel... i havent touched that tank for 6 months its pretty cool.
I've got a 40 breeder (far from monster) with a pair of Blue Acara in it. I credit my love and hate for the tank to the fact that its my never-ending work in progress; being that its my aquaponics science experiment.