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Have a Cow; the Longhorn Cowfish,
Bob Fenner
As an aquarist as well as dive-travel adventurer I have some
subjects as favorite species that I look to encounter underwater as well
as captivity. The cowfish, Lactoria cornuta is definitely among
these. It’s a great fish at any size, from pipsqueak to a foot or more.
Longhorn cowfish are cute-as-Dicken denizens of both worlds.
Cowfishes period; family Ostraciidae, are faves, although many get too
big and they have a dire downside if disturbed: ostracitoxin compounds
they produce that can have a quick and deadly effect on other fishes,
even in large systems. So, what to do? Either excludes them or read and
heed here regarding keeping yours happy. I choose the latter.
Another name for the longhorn cowfish is “hovercraft fish”; an allusion
to how this species buzzes about helicopter-wise (“ostraciiform
swimming”), waving its fins in their small openings from the hard body
casement, investigating its reef world, discovering and consuming food
items.
Cowfish Basics:
Cowfishes are part of the boxfish or trunkfish family, Ostraciidae
(Greek: “ostracum”, meaning “shell”); they’re the puffers that don’t
puff up! Their bodies are encased in hard body armor with small openings
for their fin insertions, mouth, eyes and gills. This is a great
strategy for avoiding predation, except that it makes them quite slow
and clumsy in maneuvering. Some species, like the cowfish of this
article, have further body armament, a pair of prominent spines in their
“foreheads” and another duo trailing back off their rea anal area.
Boxfishes are found worldwide on shallow reefs of the Pacific, Atlantic
and Indian Oceans. Lactoria cornuta itself occurs in the western Pacific
and through-out the warm waters and subtropical reefs of the Indian
Ocean, including east Africa’s coast and the Red Se to depths of about
165 feet.
Though caught and traded as small specimens only, due to the real
rate-limiting costs of shipping, the longhorn cowfish grows to 18 inches
in the wild, and this is “fisheries length” (not counting the actual
tail/caudal fin). Yes, this is a largish, messy fish that needs room and
good circulation and system filtration.
Although L. cornuta is by far the most popular boxfish in aquarium use,
many other choices exist- larger and smaller, and much colder water.
Lactoria cornuta can vocalize, producing grunting noises by stretching
muscles along the gas bladder. This is much the same as you rubbing your
fingers over an inflated balloon. These noises can be heard underwater
and even through aquarium system walls. Cowfishes produce vocalizations
in relation to pleasure or aggravation.
Compatibility Concerns:
Compatibility is an important issue for two reasons: 1) To ensure you
are able to get food to your cowfish and 2) To discount the likelihood
of over-upsetting this fish, causing it to release ostracitoxin, which
is toxic to fishes (ichthyotoxic). To be sure, the probability of such
poisoning is actually quite small. Most of the few events I’ve
encountered have involved the cowfish dying- getting stuck on a pump
intake, otherwise gone undiscovered dead and dissolving. Take care when
netting this species and do not dump their shipping water into your
system. Avoid housing this species with overly aggressive tankmates.
Fish I’d be ware of placing with boxfishes include moray eels, large
angelfishes, triggerfishes and some largish puffers and wrasses. I’ve
even encountered bigger basses and groupers that bossed them about to
all-s detriment.
Reciprocally, cowfishes will sample to completely chomp most all
crustaceans, mollusks, sponges, worms and some echinoderms if they’re
available and the Ostraciid is hungry or just curious. Most all fish of
size are safe from their sharp, snipping beaks, as long as they’re
healthy. Stinging-celled life (corals, anemones, etc.) is usually left
alone; in fact, juveniles of this species are often encountered and
collected in their association with Acropora corals.
Adult cowfish are solitary and territorial and should only be kept one
to a tank.
No Tank is Too Big:
Big, bigger, biggest- get the largest tank you can afford and fit in
your available space. Though not apparently very energetic, these are
massive, messy fishes that really go through a bunch of food. They are
almost always in motion; and they’re not great at making turns; so large
spaces, including width, make it easier for them to move about without
colliding into their tank or objects in the aquarium. Due to their
copious meaty foods and after effects, much blowing of water into the
sand, overall feeding and wastes produced, your system needs plenty of
circulation and biofiltration, along with regular (weekly) partial water
changes and gravel vacuuming to discount the eventual loss of water
quality. As long as water movement is diffuse, i.e., non-unidirectional,
it really can’t be too vigorous. The current need not come from an
outside pump; simple powerheads and/or submersible recirculating pumps
will serve well.
Feeding Notes:
Lactoria is an omnivore that eats various free-living invertebrates and
fish in the wild; along with a considerable amount of Foraminiferans,
worms of many sorts, mollusks etc. that they blow the sand away from,
while ingesting a good deal of substrate.
Lactoria in captivity almost all learn to accept commercial meaty foods
or frozen/defrosted mixed seafood for human consumption. Best practice
is to feed all your other fishes on one side of the system, and utilize
feeding tongs or stick to offer your cowfish food at the other end. Watch Out for Too Much Stress
and Injury:
Cowfishes and boxfishes are very tough and are generally about the
last to show signs of environmental or pathogenic disease. However they
can contract the usual parasites, e.g. Crypt and Velvet, Cryptocaryon
irritans and Amyloodinium ocellatum respectively; and like all puffers,
are sensitive to copper treatments. I encourage you to look into Quinine
compounds if/when you find yourself in a situation that calls for direct
treatment.
With unknown bumps or blobs on their skin or fins, I’d take a
wait-and-see approach, as often these are manifestations of physical
trauma (run-ins with something in the environment) or stress. Check your
system and be patient; and they will often heal in time of their own
accord.
If your cowfish goes on a feeding strike or seems to be sitting
about a good deal of the time, don’t panic! These apparent “time outs”
are quite common and almost never are cause for concern. These fish can
literally go without food for weeks, and lay about for even longer, only
to spontaneously snap out of their funk. Moving and isolating them in
small volumes is counterproductive.
More Cowfish! Reproduction:
There are no known identifiable (sexual dimorphism) or color
(dichromatism) differences between the sexes in this species. Not
bred/reared in captivity as yet; in the wild pairs are formed near
sunset, just ahead of spawning, and the eggs and young are pelagic.
Cloze:
Cowfishes, including L. cornuta, aren’t difficult to keep, with the
proviso of keeping them “happy” so they don’t release ostracotoxins.
This happy requirement is easily met by providing plenty of uncrowded
room- hundreds of gallons ultimately- and training yours on meaty foods
in a way that prevents their tankmates from stealing it all. For reward,
you’ll have a true “aqua dog” for many years as an ever-interesting,
comical pet.
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