The clownfish was the first marine aquarium fish which was bred in captivity in the 1970s. The worldwide marine aquarium industry values between $200 million to $300 million according to 2003 United Nations report. According to the American Per Products Association, American households have 1.3 million saltwater aquariums which are home to 9.3 million fish. Many of the wild fish are either imported to the U.S. or caught from the reefs of Hawaii and Florida. This is the reason some conservationists and hobbyists are worried about the reefs due to wild fish trade. The capturing of these fish result in depletion of fish population and destruction of reefs.
According to CORAL Magazine, about 300 species of fish have been bred in captivity. These fish are likely to be more healthy than salt water fish since they are given aquarium food and are less prone to diseases. This is good since ocean acidification and global warming cause large amounts of fish to die. Breeding in homes and small aquariums will prevent that.
Fishers in most countries use cyanide to stun the fish in order to catch them easily. This causes reefs to die or be wiped from the area. Despite this practice being illegal, most Asian countries still fish this way.
"Coral reefs are the productive centers of the ocean," says Judy St. Leger, the president of Rising Tide Conservation, a New York-based program under the SeaWorld & Busch Gardens Conservation Fund, which works to protect reefs by promoting captive breeding. "One way to assure that fish do not have a destructive past is to select animals from aquaculture," St. Leger says.
Blue tangs have not yet been bred in captivity due to their fear of extinction. Tangs aren't easy to find in the wild. Reefs sometimes have to be broken in order to find them. Also, there are no ways to breed them in captivity due to their difficult egg hatching methods and the struggle to keep them alive. But after the movie Finding Dory, where the titular character Dory is a Blue tang, it is worried they might become the targets of captivity. This was the case after Finding Nemo came out, where Nemo, the titular character, caused the demand for clownfish to increase.
The main reason behind keeping fish in captivity is that fisheries or large marine aquarium companies will not turn to the oceans to find fish. When that happens, many fish die and much of the coral reefs are destroyed. To prevent this, fish are bred in captivity so they are right there in little aquariums without any worry of hurting the marine ecosystem.