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What is a Longhorn Cowfish?

J.M. Densing
J.M. Densing

A longhorn cowfish, scientific name Lactoria cornuta, is a unique looking, boxy yellow fish with two long horns emerging from the front of its head as alluded to by its common name. It lives in warmer ocean waters of the Indo-Pacific region, and eats a varied diet. When under severe stress, it emits a poisonous substance called ostracitoxin. Longhorn cowfish are often kept as pets in home aquariums, but they can be difficult to maintain.

The longhorn cowfish is a medium sized fish that can grow to an average adult length of 15 to 20 inches (38 to 50 cm). It has a boxy, wide shape instead of being long and narrow like many other fish. The color can vary from an olive shade to a bright true yellow, and the fish usually has bluish white spots. It has a pair of long, light colored horns projecting from the front of its head, just above the eyes, and another pair of smaller horns in the back of its body, near the bottom. It has several tiny, almost transparent fins on its back and sides and an extremely long tail fin.

Veterinarian with a puppy
Veterinarian with a puppy

The native range of the longhorn cowfish in the Indo-Pacific stretching from the Red Sea and Eastern Africa and north to the Pacific waters near southern Japan and the Lord Howe Islands. It inhabits tropical and sub-tropical waters, and often stays in shallow coastal areas or near reefs. It's a slow moving fish that prefers to stay near available cover. As an omnivore, its diet is extremely varied and can include algae, aquatic plants, smaller fish, shrimp, worms, snails, mussels, and other small invertebrates. Young fish tend to congregate in small groups, but adults are usually solitary.

When the longhorn cowfish is feeling harassed or under a great deal of stress, it can secrete a deadly poisonous toxin. This substance is called ostracitoxin, and it is secreted along with mucous from the skin of the cowfish. This helps to protect it from predators in the wild, but it can cause problems such as killing other fish if kept in an aquarium.

Because of their unique look, longhorn cowfish are a popular choice for saltwater aquariums; they can be found in commercial facilities and in home fish tanks. They require a calm, low stress environment and should be kept only with non-aggressive neighbors in a tank that holds at least 100 gallons (378 l) of water. They should be fed several times a day with fresh food like brine shrimp or commercially prepared aquarium feed. Their teeth grow continuously, so they need some hard shelled food like snails to wear them down and maintain appropriate length. Water should be maintained at optimal temperatures and PH levels.

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      Veterinarian with a puppy