I was in PetCo the other day and noticed in one of there sw tanks they have a shark catfish (silvertip, columbian, etc. catfish - whatever you want to call them). I know these fish are brackish but the guy said that they can live in a full sw tank. I am asking b/c I have two that are about 5-6" in length now. I have them in my 55 gal sw tank - do they need to be in sw, can they be in sw, or should I just let them be. They seem to be doing fine where they are now. I just thought it was interesting and cool - since they look like "real" sharks....