Longhorn Cowfish

 Quick Care Facts

• Care Level: Expert   • Temperament: Peaceful   • Maximum Size: 20"
• Minimum Tank Size: 150 gallons   • Water Conditions: 72-80° F, dKH 8-12, pH 8.1-8.4, sg 1.020-1.025
• Diet: Omnivore   • Origin: Indo-Pacific
• Family: Ostraciidae   • Species: Boxfish   • Aquarium Type: Reef Compatible

Help Support AquariumDomain!      

• Your support keeps AquariumDomain advertisement free, lightning fast and fully optimized for both mobile and desktop browsing.

• Visit our Patreon page to learn about the exclusive benefits our Patrons receive!

Longhorn Cowfish are extremely popular with hobbyists and are most likely the first name that comes to mind when the species of Boxfish is mentioned. They are a hardy species that can be found grazing among the reefs and sand within less turbulent waters throughout the Indo-Pacific.

They are generally peaceful and have an excellent defense against predation by having horns on their foreheads as well as their rear undersides as well as having the ability to secret a venomous ostracitoxin from their already poisonous skin when stressed (ostracitoxin can also be released upon death); care should be taken to keep Longhorn Cowfish comfortable and in a low stress environment as their ostracitoxin can kill other tank inhabitants. Longhorn Cowfish can be found through online vendors, but may sometimes be hard to find; special ordering may be necessary at local retailers.

Although they may seem small at a local retailer, Longhorn Cowfish are often seen in the wild at sizes of 20", but generally only reach around 16" in an a home aquarium. They should be housed in nothing less than a 150 gallon system and be provided with plenty of live rock and live sand for shelter and grazing. They love to eat and due to this fact along with their large adult size, they can add a sizable biological load to their aquarium; strong, efficient biological and mechanical filtration is required along with a quality protein skimmer. In the wild they prefer calmer waters and should not be exposed to high, turbulent water movement (low to moderate is recommended).

Although they can be reef compatible, a FOWLR system is ultimately recommended as they will not usually harm corals or anemones, but will gladly snack on live snails, tubeworms, small shrimp, and benthic invertebrates in addition to small fish. Longhorn Cowfish are generally peaceful and should be housed with peaceful tank mates that will not cause them stress; however, they can become aggressive with conspecific tank mates and multiple specimens would need a much larger aquarium with plenty of separate territory. Choose tank mates wisely and remember that Longhorn Cowfish have the ability to release ostracitoxin into the water column.

Longhorn Cowfish are omnivorous and can be observed in the wild searching for benthic invertebrates in the sand, eat various marine algae, and snacking upon snails, tubeworms, and small fish. They are not picky eaters and in an aquarium environment they will readily accept a wide array of live, frozen, or freeze-dried, and vitamin enriched brine shrimp, mysis shrimp, bloodworms, ghost shrimp, krill, chopped clams, marine algae, mussels, silver sides, snails, and quality, Spirulina-based flake foods for carnivores, omnivores, and herbivores as well as other prepared foods. Longhorn Cowfish, like other boxfish, have teeth that are constantly growing and can be kept in check by the feeding of live snails and various live "feeder" shrimp. Feed 2-3 times a day.