Cowfish in Aquaria

Reprinted from Akwaforum September 2001
By Theresa Ulrich

The world of marine aquaria is full of awesome wonders. The veritable treasure of beautiful and exotic species is endless. However, the cowfish is one gem that is stealing the hearts of many marine aquarists.

From the first glance, it is obvious that cowfish are unique. They look like boxes that transport themselves in a mysterious manner. Upon a closer inspection, hobbyists see a gentle face adorned with beautiful blue eyes. Even more alluring, cowfish will approach the glass to return the gaze of their observers. These enchanting creatures have a curious, friendly nature that tickles the soul. It is no surprise that cowfish are becoming one the aquarium trade's most popular commodities.

Biology
There are many species of cowfish, but the one that is most commonly available in the aquarium trade is the Long horn cowfish, Lactoria cornuta. This species also is the friendliest, making it a desirable acquisition.

It is not difficult to discern how the cowfish acquired its name. The most noticeable similarity to the land bound bovine creature is the horns that cowfish possess. Cowfish have two pairs of horns. One set projects forward above each eye. The second set protrudes backward, pointing out from the ventral region. In the wild, the horns of the Long horn species typically grow longer than any other cowfish species. However, many individuals who have adapted to aquarium life have short horns. Inevitably, as cowfish adjust to glass homes, they rub or break their horns on the tank sides. The repetitive encounter with the glass results in eternally short horns for the cowfish.

Cowfish eyes also resemble their land counterparts. Their spherical eyes protrude, causing them to catch the light and appear blue. The eyes move independently, so cowfish are able to look in two different directions at the same time. The increased visual capacity is the perfect trait for a fish that constantly grazes, always searching for its next snack.

Upon closer inspection, aquarists will notice that cowfish also have unusual mouths. Their lips are thick and highly textured. They are perfect for picking up and grasping small pieces of food. Cowfish even use their lips to help them separate parts of food, allowing them to spit out the less tasty parts after the desirable ones have been chewed and swallowed.

Their teeth are thin and needle like, helping to give them excellent gripping and scraping power. With the assistance of their powerful jaws, the teeth are able to dislodge small animals that are strongly wedged on substrate or rock. The powerful teeth and jaws are also capable of cracking shells of clams and hermit crabs.

Cowfish have another unusual talent to aid them in their search for food.. They can perform hydraulic jetting, which allows them blow a stream of water into the substrate. It is an effective method for uncovering hidden prey in sandy lagoon areas. In captivity, cowfish transfer this behavior to spitting water at the surface. This is because they associate feedings with the surface of the water, the place from where aquarists typically feed their fish. In fact, it is not uncommon for cowfish to develop good aim and shoot their keepers, giving them a face full of sea water.

One of the most noticeable and distinctive features of cowfish is their body shape. Cowfish have a rigid, hard carapace from which the caudal peduncle, fins, eyes, and lips protrude. The hard, shell-like body acts as protection against predators. Unfortunately, cowfish do not have scales, so they tend to be more prone to disease than other fish. The body coloring varies from ashen yellow, to deep yellow, to olive. The color varies depending on diet, cowfish age, lighting, water conditions, and mood. The primary background color is interrupted with white or blue polka dots.

The tail contains the caudal peduncle and tail fin. For the cowfish, the tail offers excellent maneuverability. The tail acts much like a rudder of a boat, assisting the fish with their course of direction. For aquarists, the tail is a good criterion for helping to decipher cowfish age. Newly hatched cowfish exhibit merely a caudal fin. As cowfish age, their peduncle becomes much more evident. Combined the peduncle and fin will nearly equal the length of adult cowfish bodies. Hence, the longer the complete tail is in proportion to the cowfish body, the older the cowfish is.

The cowfish tail fin also unfolds itself into a beautifully decorated fan. Upon close observation, hobbyists will noticed that the fanned tail continues the pattern of yellow with white polka dots, the same as the body. Likely, the tail is another deterrent against predators in the wild. When cowfish open their tails, they appear to double in size. No doubt, the trick of seeming to instantly double in size is intimidating to other fish. Aquarists, however, can enjoy the beauty of the fanned open tail, as it quickly becomes a greeting toward cowfish keepers, rather than a warning.

Cowfish have a single caudal-ventral fin and dorsal fin. They have one pair of pectoral fins, but lack pelvic fins. Even so, cowfish have excellent maneuverability. Because cowfish fins appear nearly invisible, cowfish appear to float or glide magically in water. This special form of locomotion is called ostraciform swimming and is exhibited only by boxfish, trunkfish, and cowfish.

The rigid carapace requires a specialized gill opening as well. Rather than an operculum, or gill cover, cowfish possess a rigid gill that is merely a slit. Their unusually fast respiration is aided by the pectoral fins which flush water into the gills. This unique gill opening makes cowfish more prone to contracting parasites in their gills, however.

Cowfish are usually sold as darling juveniles of less than one inch. They are irresistible at this stage, resembling a yellow ball with slit eyes. Few young of this size will have yet grown any horns, and the hint of a tail fin is barely noticeable. Aquarists may be surprised to learn, however, that Long horn cowfish can grow quite large in a short amount of time. In the wild, they have been reported to grow up to 20 inches, with proportions close to the size of a soccer ball. Although cowfish rarely grow so large in captivity, aquarists should still expect these large fish to grow up to at least 12 inches in their aquariums. In fact, Long horn cowfish can grow up to six inches total body length within its first year of life.

Origin
Long horn cowfish are found in Indo-Pacific waters. They congregate in lagoon type of environments that are sandy with grassy patches. They appreciate open space, but also nest in their own territories within the grass beds.

Tank Set-up
Because Long horn cowfish can grow large, aquarists should not consider an aquarium of less than 75 gallons for them. However, water quality will be more stable in tanks of 125 to 180 gallons or more.

Cowfish have a high waste output and will require a strong, efficient filtration system. The wet/dry filters designed to carry large biological loads are perfect choices for cowfish tanks.

The aquarium of choice will also require a secure lid without large openings. Scared cowfish have been known to jump out of their glass homes, so it is important that the top of their aquarium is completely covered.

Flourescent lighting which simulates sun rays, but is not overly bright, will work well for cowfish tanks. Hence, lighting that displays tri-spectrum to full-spectrum rays is sufficient. Stronger lighting, such as metal halide, tends to wash out the beautiful color of cowfish. In nature, cowfish are not exposed to lighting with such great intensity, so mere flourescent tubing is more suitable.

Decor
Since Long horn cowfish appreciate open space, their tanks should not be overly filled with decor. A few rocks and plants will provide places for them to hover over without subtracting too greatly from the open space. Some live rock in the tank is a good choice. Not only will it aid in biological filtration, but it will provide nutritious live snacks, such as amphipods and crustaceans, as well. Live macro algae is a lovely thought for cowfish tanks, but it will not survive long. The cowfish will continue to nibble on macro algae until it is completely depleted.

Tank Introduction
It is important to keep stress levels of cowfish reduced. When purchasing a cowfish from an aquarium store, it is advised to bring a cooler or a dark bucket with a lid. After specimens have been bagged, they will be safely transported home in the cooler or bucket. These containers prevent the cowfish from being overly stimulated. This is important for preventing toxin release which could kill the cowfish themselves.

While acclimating the cowfish to their new home, the room of the aquarium should be darkened. The lights should be turned off and curtains drawn. The tank lights should be turned off as well. Once the cowfish has been placed in the water by following proper acclimation procedures, the lights of the aquarium should remain off until the following day.

Tank Mates
Cowfish should be kept with docile fish. This way they will feel less threatened into releasing toxin. Also, they will not have to compete strongly to get their fair share of meals.

In general cowfish do not tolerate very well other members of the same species. Males especially will bicker and quarrel; however, male and female pairs are compatible. Unfortunately, there are few cowfish species in which sex is definitive by appearance. Unless providing an extremely large aquarium in hopes of breeding one day, it is best to keep only one of each cowfish species per tank.

Although cowfish do not do well with members of their own species, there are few problems when they are kept with different species of the same Ostraciid family. For example, a Yellow Spotted Cube or a Hovercraft cowfish may reside peacefully with a Longhorn cowfish. So it is possible to create a community tank of various, single Ostraiciid plain species.

A successful community tank with other species of fish is possible as well. These fish are of the same gentle, non-aggressive disposition as cowfish. Hence, aquarists may keep a beautiful variety of species in one tank that will be compatible with their cowfish as well. Fish of similar disposition include anthias (Antiniinae), grammas (plain \i Grammatidae), chromis (Pomacentridae Chromina), flasher wrasses (Labridae paracheilinus spp.), gobies (Gobiidae) and fire fish Pterois spp.)

Surprisingly, seahorses are not a compatible tank mate for cowfish and boxfish. Seahorses have a highly specialized food requirement, and will have a difficult time getting their share of foods. Not only are cowfish quicker at nabbing food, they are more aggressive. They can even be intimidating, preventing the seahorses from seeking out food. Cowfish will also nip and pick at seahorses. Seahorses naturally grow a layer of algae upon their skin. Cowfish are attracted to the algae and the unusual locomotion of seahorses. They respond by nibbling on the seahorses, trying to determine if seahorses are a good food item. Eventually, seahorse health is compromised. No Horsing Around Cowfish offers more detailed information about seahorses as cowfish tank mates.

It is not recommended to keep cowfish in a reef tank. By nature, they snack on sessile invertebrates, clams, corals, and other tiny crustaceans. Reef keepers would be sadly disappointed to find cowfish snacking on their expensive corals and invertebrates. In fact, invertebrates are not to be added to a cowfish tank unless they are intended to become food items. Large cowfish have no trouble opening shells of gastropods, molluscs, and tiny hermit crabs. They relish decorator shrimps, crabs, starfish, duster worms, and urchins. Their needle like teeth and strong jaws are specially designed to scrape, crush, and pry. In nature, cowfish and boxfish will eat sponges, tunicates, and coral animals. Hence, any small creature that moves or has good color will intrigue cowfish appetites. (One invertebrate that does not fall victim to cowfish feedings is the horseshoe crab. Its slick shell coating is too difficult for cowfish to grasp, even with their pliable lips.)

In addition, there are some fish species that should not be kept with cowfish. Aquarists should avoid large angelfish and damsel species, triggerfish, puffers, moray eels, large dottybacks, snappers, and surgeon fishes. It is best not to keep any cleaner wrasses with cowfish either. They will likely irritate the scaleless cowfish skin.

Feeding
Cowfish may be slow to feed when newly introduced into aquaria. They can usually be brought around with offerings of live adult brine shrimp or live black worms. Once they begin to accept live foods, they will soon convert to other aquarium fair.

Cowfish should be fed an assortment of seafood, such as shrimp, krill, chopped clam, squid, mussel, fish, and octopus. In addition, they should be fed an equal amount of vegetable matter, such as dried seaweed, defrosted peas, corn, broccoli, and spirulina.

If there is no live food living in the tank, such as amphipods or copepods, then cowfish should be fed three small meals a day. If cowfish are supplied with live macro algae or cultures that live and grow in their tank, then one or two meals per day will suffice.

Maintenance
Regular water changes and substrate vacuuming must be performed on cowfish tanks. They are sensitive to imperfect water conditions, yet they produce a high biological waste load. Ammonia and nitrite levels should remain as close to 0 as possible. It will be more difficult to keep the nitrates low in a cowfish tank. As the nitrates begin to approach 40 ppm, aquarists will know that a water change is required. Another indicator for a water change need is a declining pH level. Aquarists will want to keep the pH at 8.0 or above.

Toxin
Cowfish are capable of exuding a toxin called ostracitoxin. Although the ostracitoxin is potent enough to kill off tank mates, including the cowfish themselves, poisoning events don't happen very often. Keeping appropriate tank mates and low fish ratios will help prevent toxic episodes.

Ostracitoxin episodes can be identified by unexplainable foaming on the water's surface and a general cloudiness of the aquarium water not due to other causes. The affected fish will hover or sink to the bottom, perhaps losing their balance, and begin to breath laboriously.

If rescued immediately after release of ostracitoxin, fish can be saved by being immediately removed from the toxic water and placed into an untainted source. To re-establish safe water, the affected tank will require a 50% water change. New carbon and a poly-filter pad should also be run in the tank or filtration system for two days. At the end of the two day treatment, the carbon and poly-filter pad should be discarded, and the tank will then be safe for inhabitants.

Keeping carbon in the cowfish tank or filtration system is a primary preventative to losses after ostracitoxin is released.

Disease
Cowfish are prone to a few parasite, fungal, and viral diseases. In particular they are susceptible to Cryptocaryon irritans, saltwater ich, and Amyloodinium ocellatum, marine velvet. These are parasites that cowfish likely harbor naturally in their intestinal tracts. The parasites appear when the fish have a weakened immune response. This can occur from water changes with water that does not match tank water conditions. The disease outbreak can also be a result of stress. Harassment from other fish can greatly stress cowfish.

There are a few hot pepper-mint based treatments that work very well for external parasite diseases on cowfish. They cause the stress coat to slough off at an increased rate, taking the parasites along with it. Hence, the parasites are not provided with adequate time to reproduce on the host, and their cycle is broken.

Cowfish are also at risk for fungal infections. If they have injuries, especially from broken horns, variances in water temperature can result in a fungal infection. Most marine fungus infections are a variant of bacterial infection. Treatments os Neosporin rubbed on the inflicted area have wonderful results. Simply massage some oinment onto the infected areas while the fish is out of water. Perform this treatment once or twice a day for 10 days, or until the fungus has been absent for 3 days.

Finally, cowfish may develop large, cauliflower looking white cysts called Lymphocysts. These viral clumps are harmless and will dissipate on their own over time. However, a series of daily, freshwater dips can speed the healing process.

Many of the illnesses that affect cowfish can be limited or controlled by adding Ultra-violet sterilization to the cowfish tank or filtration system. This type of filtration is particularly effective in reducing parasitic outbreaks.

Mates
In the wild, male cowfish exhibit haremic behavior. Each male has several females within his territory that he guards diligently. Females keep to their limited, rock-laden areas. The male checks on his females several times daily at females' "homes."

Breeding
During spawning season, approximately April through October, the males will spawn several times with each of his females. As he approaches their "rendez-vous" rock, he will demonstrate aggressive behavior by biting his mates. The females are forced into submission and must then spawn with their male.

The couple will rise up the water column as much as 30 meters where they will suddenly stop and back into each other. The pair will curl their tails into their bodies, line up their posterior regions, and simultaneously release their sex cells. After the event, the male will seek out the next female in his harem and start the entire process once again.

Captive Breeding
There are yet only rumors of cowfish breeding in captivity. The large rise that cowfish perform in nature make it unlikely that they will reproduce in a home aquarium. There is a stronger possibility of captive breeding in a very large tank that a public aquarium, for example, may be able to offer.

However, optimistic and dedicated aquarists may want to try breeding their cowfish to see if captive breeding can be performed. With the many changes in legislature and laws affecting wild caught marine life, there is reason to fear that someday cowfish may not be available from wild sources.

Those interested in breeding cowfish would do well to provide their specimens with the largest aquarium they could afford and maintaining excellent water conditions. The cowfish should be fed a variety of high quality foods. Food should be enriched once a week, and during spawning season, live foods should be fed at least a couple of time per week. In addition, tank lights should be left on at least ten to twelve hours per day, to simulate the longer day light hours of the breeding season.

Of course, at least one pair is required for breeding purposes. Currently, there are no reliable physical indicators to determine cowfish sex; however, some criteria may increase the chances of accurately choosing potential pairs.

Females may appear more rounded in the sides with thick lips. Males may appear more slender in the sides and have thin lips that protrude more noticeably than the females. These characteristics are only a guess of sex, based on observation of cowfish socialization and interaction. To increase the chances of acquiring at least one pair, aquarists may want to purchase as many as six cowfish in hopes that at least two of the fish will pair off.

Rearing Young
Although cowfish have not yet been bred in captivity, cowfish eggs from the wild have been successfully hatched and the fry reared. The eggs were hatched in a bare aquarium with only an air stone. The newly hatched larva were able to accept newly hatched brine shrimp. Although, the fry were raised successfully on this diet, it is recommended that the fry's diet be supplemented with copepods for assured success.

Conclusion
Following some basic practices can increase enjoyment and success with cowfish. These fish will quickly become the family pet as they exhibit their fun behaviors, such as blowing into substrate, spitting water, or greeting aquarists with their beautiful fanned tails. With some dedication and luck, some of us may see our own specimens live on in captive bred generations.

Discussions about cowfish and related species can be viewed at the Internet discussion group Cowfish, Puffers, and More. Their group can be accessed at the following URL: http://groups.yahoo.com/group/CowfishPuffers_andMore

Best of luck to us all!

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