damsels are very agressive and are highly not recommended because they usually bully many fish in the tank, even if the fish they are picking on is bigger than them! There is much research to go into have a saltwater or reef tank whatever you choose to go with. Many people like to start with nano aquariums to get lots of corals and some small fish and/or inverts, or jst a FOWLR
=fish only with live rock. Here is a link for marine fish with some info. Here to help and good luck!
Saltwater Fish: Marine Aquarium Fish for Saltwater Aquariums