i used to keep marine aquariums. you cant keep these, sorry. the closest thing you can get is a seahorse. and that is a BIG responsibility aswell. and even if the seadragon was a tropical fish, you couldn't have coral with is anyway, besides a few soft ones like mushrooms or xenia (commonly in seahorse tanks) because seahorses and leafy sea dragons like SLOOW water and coral like its fast. plus it would be stung and killed by most coral.