Longhorn Cowfish ~ Long-horned Cowfish

Family: Ostraciidae Picture of a Cowfish, Lactoria cornutaLactoria cornutaPhoto © Animal-World: Courtesy David Brough
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I have a long horn cow fish have had it about 2 months I noticed today that he is sitting on the bottom a lot does this mean he is sick.  lesha

   Probably the most well known of the boxfish! The Cowfish, Longhorn Cowfish, or Long-horned Cowfish can be seen in almost every public aquarium. They are hardy and they love to eat!

   The Cowfish, Longhorn Cowfish, or Long-horned Cowfish are easily recognized by the horns on the forehead and the bottom rear of the body. These horns make them hard for predators to swallow. In any case their flesh is poisonous and would not make for a very good meal!

  NOTE: The Cowfishes in the genus Lactoria, especially this Cowfish, Longhorn Cowfish, or Long-horned Cowfish must be dealt with carefully. If overly harrassed or stressed, it can release the toxic substance, ostracitoxin. This is a response to stress and can poison your tank. Make sure you keep this fish in a comfortable and not overly stressed environment, and keep it well fed!

For more Information on keeping this fish see:
Guide to a Happy, Healthy Marine Aquarium

  • Kingdom: Animalia
  • Phylum: Chordata
  • Class: Actinopterygii
  • Order: Tetraodontiformes
  • Family: Ostraciidae
  • Genus: Lactoria
  • Species: cornuta
Cowfish Adult, Longhorn Cowfish, Lactoria cornuta
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Cowfish in captivity

The Longhorn Cowfish is a spectacular specimen, having a unique look, coloring and interesting movements that are mesmerizing! This little guy will eventually grow to 20," needing a tank that is at least 250 gallons. Keep with peaceful fish that will not stress them out, since they will poison the tank when they are stressed or if they die. A really good filtration can help in that area, as well as having another tank set up to transfer all inhabitants if that does happen. Have plenty of carbon standing by as well as media that can filter out toxins if this happens. Cowfish nibble on tube worms and if they settle in they will live a long time, dining on veggie matter and meaty foods. Being slow eaters, other fish should not outcompete them for food like large wrasses. They are best for intermediate to advanced aquarists since they have a hard time in the beginning of their captivity.

Cowfish tiny baby, Longhorn Cowfish, Lactoria cornuta
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Tiny juvenile eating brine shrimp

This little guy is just beyond adorable and will eventually become 20" long. Their body becomes more elongated as they age (see adult video) and they will need a very large tank. Live foods may be needed to induce a feeding response. Gut load any live mysis or live brine with good nutritious food about 1/2 hour before feeding so the little moo-moo gets a quality meal! Have a crop of algae for them to feed from as well. The name Cowfish comes from the long horn like projections on each side of their heads. As a tiny baby, such as this little "calf," the horns have not formed yet, however, these horns max out then stay the same size, so as they become full grown adults, the horns appear "smaller" although they are the same. Place with very peaceful fish and keep stress levels low to prevent tank poisoning.

Cowfish Juvenile, Longhorn Cowfish, Lactoria cornuta
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Juvenile Cowfish being hand fed

This age, when their horns are long is where the name Longhorn Cowfish comes from. Although yellow as babies and juveniles, once they are adults they are not as bright yellow, but they still have their "sunny" personality! Like little tiny boxy water dogs, these fish endear themselves to their owners who rightly keep them in a 250 gallon tank with very peaceful tank mates. They can be startled if the room is completely dark and the lights come on, forcing them to "flee" which can cause them to get caught up in decorations and rock. This stress can cause them to release a toxin that can poison the tank! Like having a standard Poodle, which stress and act out in a loud and/or busy household....... if you keep everything calm, your Cowfish will be fine!

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Maintenance difficulty:    The Cowfish, Longhorn Cowfish, or Long-horned Cowfish is easy to keep. Boxfish are not challenging if you feed young specimens several times a day. Start with brine shrimp.
  The puffer's teeth will continually grow throughout its life so you will need to supplement their diet with some hard shelled foods. Occasionally offering foods such as live ghost shrimp and various live snails will keep their teeth worn down.

Maintenance:    Feed all kinds of live and frozen foods. The boxfish also eats greenstuffs. Best to feed small amounts several times a day. We generally feed squid, shrimp (the same kind people eat), mussels, and all kinds of chopped up fish. Be sure to wash these foods thoroughly before feeding. A good vegetable formula like Formula II is also beneficial. Live fish will also be taken but should not be fed exclusively.

Habitat: Natural geographic location:    Cowfish, Longhorn Cowfish, or Long-horned Cowfish are found in the Indo-Pacific: Red Sea and East Africa to the Marquesan and Tuamoto islands, north to southern Japan, south to Lord Howe Island. Inhabits inshore on coastal muddy or sandy habitats in still bays, and commonly found in harbours and estuaries. Small juveniles on protected shallow mudflats. Found in weedy areas near rocks or reefs. Juveniles often near river mouths and in brackish water. Adults are solitary, juveniles often form small groups. Large adults are shy. Feeds on benthic invertebrates by blowing away the sand

Foods:    All kinds of meaty foods and greenstuffs. A bottom feeder. Puffers are primarily predatory fish in the wild though they do graze on a bit of algae. This puffer will enjoy all kinds of meaty foods including shrimp, worms, clams, various mussels, snails, tunicates, and fish.They are not picky eaters and will quickly become adapted to a variety of prepared aquarium foods and an occasional algae wafer. Flake food is not recommended. Even though they may eat it, puffers will not thrive on it.

Social Behaviors:    Apparently this fish is sometimes aggressive and sometimes not. Keep an eye on newcomers with an established boxfish and any new boxfish that are added to the aquarium.

Sex: Sexual differences:    Apparently many boxfish are easy to sex but we haven't found this information yet.

Light: Recommended light levels:    No special requirements.

Temperature:    No special requirements. Normal temperatures for marine fish is between 74 and 79 degrees Fahrenheit.

Length/Diameter of fish:    Cowfish, Longhorn Cowfish, or Long-horned Cowfish adults can grow to 50.0 cm (20 inches). They usually only get about 40.0 cm (16 inches) in aquariums. Their size can be deceiving since they are usually very small at the pet stores.

Minimum Tank Length/Size:    A minimum 100 gallon aquarium is recommended.

Water Movement: Weak, Moderate, Strong    No special requirements.

Water Region: Top, Middle, Bottom    No special requirements.

Availability:    This fish is available from time to time.

Lastest Animal Stories on Cowfish

lesha - 2017-10-30
I have a long horn cow fish have had it about 2 months I noticed today that he is sitting on the bottom a lot does this mean he is sick.

NYCMEDICCOH - 2010-12-09
Just bought my first cowfish today he's about 4 inches long and very different looking. My kids and I like him everything seems to me going alright for now my other fish aren't harassing him too much. He's in an aggressive tank and he came from an aggressive tank with a clown trigger. I've read the horror stories hope I'm not going to be the producer of one.

  • Charlie Roche - 2011-08-19
    Article attached and sometimes agressive and sometimes not - keep an eye out. If it will fit in his mouth - he will probably eat it
  • Dani - 2017-03-24
    Hi..been six years since you wrote this.. How's your cow fish doing? I'm taking one home as we speak and also going in an aggressive tank..all the experience I have read have said theirs never release any toxin when stressed or when they died ..and a marine biologist said their reputation is a myth..
  • Eliza - 2017-09-11
    Hey! How's it going with the cowfish? I hope your fishes still aren't harassing the little guy too much... I bet it's okay for him to be harassed a LITTLE, but you know, i hope that it is NOT TOO MUCH! Make sure the harassment isn't about how different looking he is.
Kuba - 2011-05-31
If I buy cow fish as a baby can i keep him in 28 gal nano cube?
How long i can have him for ?
I heard they grow up slowly.

  • Charlie Roche - 2011-05-31
    28 gallons is big enough as the cow fish will supposedly be 20 inches as an adult. Figure one inch of fish (as an adult) for each gallong of water. 20 inches so at least 20 gallons as you have to subtract for plants and flooring and decorations. Leave your question up and I would look into this a little more cuz some say problems with these nano cubes.
  • Krista - 2011-09-14
    No. 28 gallons is not big enough. The Longhorn Cowfish needs at least 100-150 gallons at full length. Even as a baby 28 gallons won't be big enough and he will probably die and poison everything else in your tank.
  • Eliza - 2017-09-11
    I've heard that your cowfish has growing A LOT!!! I'm not sure if that is normal. Maybe bring it to a vet.
  • Kristy - 2017-09-11
    Eliza is definitely right. You know what they say... the smaller the better!
  • Eliza - 2017-09-11
    Hahaha! Thx for supporting my comet Kristy! The smaller the better is always correct when it comes to fishees
Lisa - 2012-03-26
I have had a cowfish for one year now. He is in a 95 gallon tank. Started in a 29 g nano. He is now 9 inches long. He is the most important fish in my tank. He is housed with other fish, but I have not purchased anything I am afraid to lose due to the stories of them being toxic if stressed or dying. With that said, I love this fish. What is most important to them is food!! I feed 3 to 4 times a day. 4 brine am. Then pellets and flake and repeat with 3 brine and one mysis then flakes and pellets again. I stretch the feeding out so he has fun and I also turn of side blowers so he doesn't have to chase rhe food to much. He does get irritated at times and gets patches of black. Usually because I am visiting him without food!! He spits water. Splashes water and is truly entertaining. I highly recommend this fish if you don't work and be there for it and feed it ALOT!! It really can get large so I have heard and I hope I don't have to deal with that issue to soon. They are NOT just fish. They
are pets. They recognize you and expect alot of your attention. If you can't do that then pass. Otherwise you will lose it.

  • Dani - 2017-03-24
    Hi Lisa, just found this thread. RE cow fish.. Been doing lots of research and yet to find any evidence to suggest they will release toxins whdh stressed or when they die..i have found over 100 comments on different websites RE people saying they have lost a cow fish and never lost any fish because of it..

    How's your cow fish doing ? On my way home with one and cant wait to place him in my 300 gallon tank