As far as that link to the Red Tail Barracuda - They are freshwater fish but can be acclimated to saltwater. I had one many years ago before I went saltwater, and it's probably one of my favorite fish i've ever owned. They don't get very big and they are totally bad assed - really awesome fish. Anyway, my buddy who worked at a local fish store and was a hardcore reefer. He loved mine and ended up buying one and slowly and successfully acclimated him to saltwater and introduced him to his aggressive tank. He told me he dripped saltwater and slowly raised the salinity until he was swimming in a full fledged saltwater tank. I lost touch with him shortly after so I can only be certain that I saw him in a saltwater tank ONE day....not sure how long he lasted.