The longhorn cowfish is a type of boxfish and is also known as the horned boxfish. The scientific name is Lactoria cornuta.
They are a saltwater fish native to tropical and subtropical waters of the Indo-Pacific including the Red Sea, East and South Africa, Indonesia, Marquesas, South Korea, Japan, Tuamotus, Ryukyu Islands, Australia, and Lord Howe Island. They live up to 160 feet (50 meters) deep in coral reefs, reef flats, and protected seaward reefs.
Longhorn cowfish are most recognizable by their horns on the front of their head, kind of like those of a cow or bull. When they are first born, they do not have their horns and these develop over time. It is believed their horns make them difficult to swallow by predators. Their horns are made of collagen fibers and are mostly hollow. If they are damaged, they can grow back.
The longhorn cowfish can grow up to 20 inches long. In the wild, they can live 8-10 years and a bit less in captivity.
They are slow swimmers so are not able to escape from predators quickly. When stressed, they will release a deadly toxin from the mucous secretions of their skin. It is similar to the toxin of sea cucumbers. When this fish is kept in an aquarium, its toxin can kill everything else in the tank including the cowfish itself as they are not immune to their own toxin. In the wild, they would be able to swim away from the toxic area, but in an aquarium they are not able to do so.
They are omnivorous and their diet includes algae and other organisms found in the sandy substrate on the ocean floor, which they obtain by blowing jets of water into the sand. They also eat mollusks, small crustaceans, small fish, worms, sponges, and other invertebrates.
The longhorn cowfish is sometimes kept as a pet. Their care level is considered difficult or expert level, and a full-grown longhorn cowfish requires an aquarium of at minimum 250 gallons.
Here is a video of a longhorn cowfish looking for food in the sand.