Many sharks, like the leopard shark, shown above, can grow up to 6.5 ft. long and require a minimum 400 gallon tank. You would think that the size of these fish would keep them out of the aquarium hobby industry but young, small, sharks are still offered for sale to people who may not realize how big they can get. Usually though they will not attack healthy, normal acting fish but will be attracted by the smell of blood or raw meat. They will also sense fish that are acting abnormally, like goldfish in saltwater, and try to catch them. Some sharks are constantly moving and searching for food, like the Leopard shark found on the West Coast of the USA T. semifasciatus , while others, like the Leopard shark found in the Coral Sea, S. fasciatum , lie around waiting for food to come to them.
All sharks swim by moving their vertically oriented tail fin from side to side.
In contrast, porpoise and dolphin have a horizontally oriented caudal fin which they move up and down. Most sharks are rather large and not well suited to life in captivity. Fish, squid, shrimp, occasional live goldfish. Will eat most anything they can swallow in one bite.