Description This catfish is named for the way it looks as it swims through the water. It’s shark like swimming motion with it’s high dorsal fin gives it an intimidating look. The Blackfin shark is not an aggressive fish, but it does have a very large appetite. It also has a fairly large size. This combination makes it necessary to house this fish with fish at least 2″ or larger. Also, because this fish is a catfish, it lacks scales and requires some salt in the water to help keep it healthy. Usually, 1 table spoon of salt for every gallon of aquarium water would suffice. The Blackfin shark would also live very comfortably in a Brackish water aquarium.