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What is it that soars like a parakeet, is as beautifully marked as any butterfly, has a "beak" like a macaw and is a major source of fine coral sand? Give up? It's the Parrotfishes, family Scaridae.
This group would seem to have everything going for it as far as desirability to marine aquarists; many are spectacularly colorful, they have almost comical fusiform-torpedo body shapes, and are numerous and easy to catch (at night) as they lay sleeping with or without their fish-made mucus cocoons.
Their only downside, and it's a big one, is that Scarids rarely live for anytime in captivity(!); either starving to death for reasons that will become obvious, or "stressing" out to extremes due to other rigors of captivity. Let's cover some of the science and captive maintenance notes of this group to gain appreciation and offer insights to parrotfish selection and care.
Scarids are all marine, mainly tropical in the Atlantic, Indian and Pacific Oceans. They have non-protractile mouths with coalesced jaw teeth resembling a parrot's beak. Like the related wrasses they sport large cycloid scales, large, thick caudal peduncles (the part of the body right before the tail fin) and broadly truncate (square) caudal fins. According to Nelson (1994) there are currently nine genera with eighty three reliably described species. Due to radical changes in color and markings consequent with sexual stage developments there are many nominal, mis-identified species. I'll try to make this clearer under the "sex and the single parrotfish" heading below.
Parrotfishes are closely related to the popular aquarium fish family Labridae, the wrasses. They are collective members of the Sub-Order Labroidei in the largest living Order of fishes, the Perciformes. An interesting higher classification note here for those so inclined; Nelson (94) recognizes the cichlids, Surfperches (family Embiotocidae) and damselfishes (Pomacentridae) as part of the Labroidei as well. See Joe's references in the third edition for further discussion for more.
Species of Use/Disuse:
Genus Bulbometopon: One species, a big one.
Genus Calotomus: Five species.
Genus Cetoscarus: Two species according to FishBase.org. Commonly used, almost always dead within weeks. This oh-so cute juvenile of white, bold yellow/gold and black markings is just a baby of an eventually much larger species.
Genus Hipposcarus: Two species.
Genus Nicholsina: two species
A common misunderstanding with this group is what they eat. They rarely feed on actual live corals tissue, but stomach-contents analyses have shown they do derive most of their nourishment from scraping organisms, mainly algae, living in and amongst dead coral substrates. Please see the accompanying image of how this is accomplished. Yes, they do chew off the live and dead heads of corals in gathering this material.
Some aquaristic writers have listed snails, crustaceans, shellfish and urchins as real and potential food items for captive care. Maybe a successful long-term approach to feeding these species might take the form of algae etc. mashed food being somehow applied to coral skeletons...
Okay, I'll come clean; I made up the word aquariogenic. I'm looking for a term to describe the imposed consequences of captive care in fish tanks; effects that are different in kind or extreme due to aquarium versus wild conditions. You know what we're getting at here; some species, sizes, sexes, individuals do much better in aquaria than others.
One way of discerning which varieties may be better for aquaria is observing them in their natural environs. Watching our aquatic charges on the reef yields much valuable behavioral information. Parrots are wide-ranging, sometimes covering several hundred square meters in the course of one scuba-dive observation period. This wide travel may be a matter of searching through enough necessary foraging space; allowing favorable foodstuffs to recover.
Obviously, in captivity such large areas are unavailable and apparently exert a dunning effect of parrotfish vitality. They go from extreme extro- to intro-verts, settled on the tank bottom, whereas Parrotfishes are in almost constant search/eating mode on the reef during the day, stopping, "sleeping" only at night.
Other Items of Interest:
Places I've been to in the world (e.g. Tahiti, Baja Mexico) offer Parrotfishes as regular table fare (see the picture of split-dried parrots for sale in Lombok, Indonesia). At some localities (the leeward side of some Caribbean Islands) people eat them seasonally; in other areas (parts of the Indo-Pacific) parrots are carefully excluded as being a source of ciguatera, food-fish poisoning. Scarid toxicity appears to be a matter of bioaccumulation of poisonous algal proteins.
How much substrate do you want to have in your marine system? In the course of breaking off, scraping and pharyngeal grinding coral skeletal material Parrotfishes excrete large quantities, veritable showers of coral sand. I'd seriously venture that the Parrotfishes of the world egest several thousands of tons of such material a day. Amazing, eh?
Sex and the Single Parrotfish: Like the wrasses, most parrots have proven to be protogynous hermaphrodites (both functional sexes, females turning into males); but as they say on late night TV. advertisements, "But wait, there's more". Imagine you're looking at all the Parrotfishes on Earth. You have some notion of what a "species concept" is all about and structurally and genetically and biochemically and any-other-else-ally there are distinct (sort of) "types" of Parrotfishes separate from other "types". But color and marking-wise within these species-types there is some widely differing "sub-types". Well, it turns out there are about four, five of these per species.
Now follow me here; there's 1) undifferentiated immature individuals, 2) one's that have developed into females, 3) those that have gone through being females and are now males, 4) some that are/were "just" males, and finally, 5) Super males, typically larger, most brightly colored "alpha" types. Though unlike some wrasse species, they don't' change much morphologically (structurally) with sex switching, parrots frequently have striking color differences with different age, social status and gender. Large, colorful supermales must be seen in person in the wild to be fully appreciated.
Whew, easy huh? Now you can see where the confusion has come from in accurately detailing whose who species-wise.
How do we know all this is so? Some clever weird-science researchers have shot up Parrotfishes with sexual hormones and cataloged their subsequent changes. Ho-boy. That and bunches of diver reconnaissance.
If you're determined to try a member of this family here are my suggestions:
1) Engage as large a system as you can; a hundred gallons plus.
2) The more established the tank, that is, with mature algae growth, the better.
3) Buy a small species; (some get to over three feet in length), at a small size; four to six inches. Three smaller favorites are the queen parrot, Scarus vetula, the spotlight parrot, Sparisoma viride and the bicolor parrotfish Cetoscarus (Bulbometopon) bicolor.
4) Do try to get your specimen as fresh from the sea as possible. The longer the fish stays in transit from the collector, wholesaler, and retailer to you the worse. It's just getting more starved and stressed.
5) Offer a variety of homemade and/or prepared food items along with sufficient fresh material and monitor their acceptance. Open, but leave krill, shrimp, clams, mussels and the like in their shell for calcium intake and tooth wear. Try offering these foods at the "top" of your habitat (coral, rock); this is where parrots feed on the reef.
6) Provide vigorous circulation and filtration as Scarids are avid eaters and prodigious producers of body mucus, especially the species that spin their nightly sleep cocoons; which brings up...
7) Make preparation for a suitable hiding and sleeping space; a nice coral or base rock cave with low illumination.
8) Just get one. They don't get lonely, but may fight and do get big. Usually, you'll end up with a colorful male.
9) Because of their non-competitive nature don't mix with aggressive, food-greedy species like large basses and large damsels.
Most species and individual Parrotfishes are difficult if not impossible to keep for very long under "typical" (i.e. small) aquarium conditions. In the wild they are found continuously roving, grazing stony corals, gnawing and scraping at these dead coral substrates for their algal growth, and generating copious amounts of fine coral sand.
In low-volume tanks they waste away, skulking in a dark corner possibly dreaming of happier days scouring the reefs. My advice is to instead seek out and enjoy one of the many hardy, related wrasses. Several varieties of these fare very well in marine aquaria. Leave the parrots to cruise their coral palms, making us more sand.
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Spies, Gunther, 1990. Sand Factories- the Parrotfishes. Tropical Fish Hobbyist, 4/90.
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(part of upcoming "guide called the Responsible Marine