Candy canes, mushrooms, zoos, kenya trees, frogspawn and hammers can be by each other but will sting other corals, for instance I just had my frogspawn to close to my blastos and they killed it. Someone suggested acans, I wouldn't place these in a nano close to other corals, they can be quite vicious. Lobo or trachys brains should be alright, I wouldn't trust a favia though. Clove polyps, gorgs. It all depends on the size of the nano though technically all my tanks are "nano" and I have all the corals I listed plus many more.