Considering the total number of species, diversity, available selection, and beauty of Labrid fish in the marine aquarium trade, it should be no surprise that every few months this column would feature a new genus of wrasses. Thus, the genus Coris will represent the first edition of wrasses in 2005. This genus is diverse: some of its members do well in reef aquariums, while others would terrorize the same system. Likewise, a few species remain small enough to be easily kept in many home aquariums, while other members of this genus can become 100-pound behemoths. Clearly, careful selection is necessary to maintain these attractive fish that the marine aquarium trade has dubbed the Rainbow Wrasses.

Meet the Family

Coris is one genus in the second largest marine fish family, Labridae. This huge family contains more than 65 genera and 460 species. The fishes placed in the Labridae family characteristically use their pectoral fins extensively for swimming, rarely using their tail, and then usually as a means of escaping danger. Some species are among the most popular marine aquarium fishes found in home aquariums.

At the beginning of the 19th century Lacepede (1801) introduced the new genus Coris. His description was based on collections of a wide-ranging Indo-Pacific species, C. aygula. Although this fish was labeled as the first species of the genus, it was, in fact, the second fish of the genus to be described. The first described species was initially assigned to the genus Labrus as Labrus julis (Linnaeus, 1758). As the first person to describe animals using the binomial nomenclature now in use, Linnaeus often was too inclusive, lumping together animals that later specialists would separate into different groups. As an example, Lacepede created the genus Coris and provided a proper home for this species. Fish of species in this genus are notable, however, for undergoing a magnificent color change as they age from juveniles to adults. Despite their easy generic classification, ichthyologists were often bewildered by the task of assigning a species name because of their odd color forms. As a result, many species have been described many times. For instance, C. aygula has 11 synonyms assigned to it, while C. julis has 15 (Randall, 1999). All told, once sorted and studied, the genus Coris tallies 27 species.

Missing from the above list are fish from the genera Pseudocoris and Ophthalmolepis. In the past, the five species of Pseudocoris and the single species of the genus Ophthalmolepis were regarded as members of the genus Coris. The lunate caudal fin found in Pseudocoris, however, is absent in all Coris species. Additionally, their propensity to consume zooplankton from mid-water is unlike the feeding characteristics typical of Coris. Furthermore, the different dining lifestyle is further revealed by a few montable features, most notably a reduced jaw and pharyngeal dentition, aiding in the capture of swimming or passing food items. In much the same fashion, a different vertebrae and dorsal ray count, along with larger dorsal and anal pterygiophores (the bones with which the fins join the body), have helped to keep Ophthalmolepis as a distinctly recognized genus as well.

Little variation is present in their dorsal, anal, and pectoral fin ray counts. Generally, Coris species have 12 hard dorsal rays; however C. batuensis and C. variegata, possess only 11. Anal rays typically number 12, except for the two aforementioned species, which may occasionally have 11. Additionally, they almost always have 13 or 14 pectoral rays, but on rare occasions ichthyologists have noted 12 and 15 as well. The mouth also presents a series of consistent features that distinguish this genus. A pair of large canine teeth are located at the tip of both the upper and lower jaws. These teeth are slightly recurved and fit nicely into one another when the jaws are closed. Running the length of their jaws are several rows of teeth. Beginning as large conical teeth, the outside row gets progressively smaller as the row extends toward the rear of the mouth. Inside these conical teeth are small, molariform teeth, which form several more irregular rows. The final teeth of note are their pharyngeal teeth. These bone-crushing teeth are used by several genera of Labrids, including Macropharyngodon and Halichoeres. These teeth are especially useful for crushing the hard exoskeleton of motile invertebrates such as hermit crabs, echinoderms, and mollusks (Randall, 1999).

Randall (1999) further organized the genus with a single complex (listed below) of closely related species. Although not listed in the Caudimacula complex, it is believed C. hewetti may belong to this complex due to its juvenile coloration, which is similar to other species in the Caudimacula complex. Additionally, C. ballieui, C. centralis and C. flavovittata are not closely related to any of the other Coris species; thus they are listed as relics. Finally, it's entirely possible that further DNA research will prove that C. musume and C. picta are closely-related enough to consider them subspecies. For aquarists, however, given most species' striking coloration, most anyone equipped with a photographic identification guide can easily make an accurate ID in most cases.

In the Wild

Coris species are represented in both the Atlantic and the Pacific Oceans, although they are considerably more plentiful in Pacific waters. It was originally believed that only one species, Coris julis, was found in the Atlantic, having an extensive geographical range extending from Norway to the equator. However, Seret and Opic (1986) discovered that this wide-ranging Atlantic species was actually two species and therefore named one species C. atlantica. It is now believed that any Coris species located south of the Verde Islands are C. atlantica. All remaining Coris species are found in Pacific waters. Despite the wide range of the two Atlantic species, the Pacific species remain localized with a number of species having been collected from only one or two locales. Coris nigrotaenia is one such species, known only from the Gulf of Aden; Coris hewetti is another such example, having been found only at the Marquesas Islands. Perhaps the rarest of all species is C. debueni, as it is known only from Easter Island. A Hawaiian endemic is also present in this genus. Although it's more prevalent at the northwestern edge of this chain of islands, C. flavovittata can be found extending all the way northward to Kure Island. Because of the often limited distribution of Pacific species, it is perhaps ironic that C. aygula has the largest distribution of the genus. Species have been collected from the Red Sea and eastern coast of Africa, from southern Japan to southern Australia, and as far east as the Ducie Atoll.

The majority of Coris wrasses can be found in fairly shallow water as juveniles. It is common for specimens to be numerous at depths of only 5 - 10'. The larger individuals, however, generally prefer water slightly deeper, often between 40 - 120' deep. Deeper dwelling individuals exist, though, as submarine observations have identified Coris gaimard as deep as 240' (Chave and Mundy, 1994), and deep water fish traps have captured C. ballieui at these same depths (Randall, 1999).

	Coris dorsomacula, called the Pink-lined Rainobow wrasse within the aquarium trade, is a wide-ranging Pacific species. Although not regularly collected for the hobby, juveniles do have a tendency to appear at the local stores on occasion. Top photo (male), bottom (female). Photos courtesy of John Randall.

Fringing reefs, on either the ocean side or lagoonal side, are the overwhelming choice of the fish in this genus, although they occasionally can be found roaming grass beds. Individuals will cruise open stretches of sand adjacent to the reefs. While the reef presents various food options, the sand offers Coris species their security. It is a delicate balance that they master extremely well. Rainbow wrasses utilize the sandbed both for sleeping and safety, and they are noted to maintain several preferred "sand diving" areas throughout their home range. They will remove larger stones and rocks leaving only a soft, micro-fine sandbed which allows for easy "sand diving." As nightfall approaches, the wrasse will retire into the sand for the evening only to rise again shortly after sunrise. Likewise, it uses this same disappearing trick to escape imminent danger. When threatened, the wrasse can dive into the sand literally "in the blink of an eye." The largest adults are an exception to this rule; they may opt, instead, to wedge themselves in between rocks. Presumably, the adult fishes' large size may hinder their attempts to disappear quickly.

Another Coris wrasse noted to clean adult fish, even other adult Coris species, is C. sandeyeri, also called the King Rainbow wrasse. A male is seen in the top photo, a juvenile in the bottom picture. Photos courtesy of John Randall.

As mentioned earlier, the morphological features of the Rainbow wrasse's mouth enable it to capture and consume hard-shelled invertebrates. Their lifestyle and security dictate the need for open stretches of sandbed. It should be no surprise, therefore, to learn their stomach contents are often filled mostly with sand-dwelling gastropods. In one study a 4" Coris aygula had stomach contents consisting of over 60% gastropods, 10% hermit crabs, 10% isopods and 10% chitons (Sano et al, 1984). Adult individuals of the same species over 10" long have been noted to consume mostly hermit crabs and mollusks (Randall et al, 1990). Juveniles of another species, C. gaimard, are noted to consume mollusks for over 70% of their diet (Hobson, 1974), while the adults shift to a more varied diet of brachyuran crabs (33%), gastropods (31%), pelecypods (22%) and hermit crabs (12%) (Randall, 1999). Rainbow wrasses are not afraid to exert some energy to look for food, either. Adults will regularly flip over rocks searching for food. Additionally, juveniles will often act as cleaner fish by removing parasitic infections from larger fishes (Ayling and Cox, 1982).

The majority of Coris species remain in small harems consisting of a single large adult male and several smaller juvenile and female fish. Species known to cruise lagoons, however, are more often seen as solitary individuals. As with all protogynous hermaphrodites, the female's ovaries will become virtually non-existent while the male sexual reproductive organs, most notably the testes, will mature into functional organs. This, of course, only happens within a harem after the male's demise. However, not all male Coris wrasses are the result of a female-to-male sex change. Coris julis has been noted to be diandric. This means that the genus has been shown to have both primary and secondary males, or in other words, some males are, in fact, born as males and are not the result of a female-to-male sex change. Up to 30% of the Coris julis sampled were found to be primary males that displayed a drab initial phase (normally, this initial color phase is associated with females) (Roede, 1966; Randall, 1999). As of yet, none of the Pacific species have been shown to be diandric.

	The most common fish found around Easter Island is Coris debueni. However, this also happens to be the only locality this fish is known from. Thus, it was dubbed the Easter Island Rainbow wrasse. Top left (female), top right (male), bottom left (juvenile). Photos courtesy of John Randall.

In the Home Aquarium

If I were to say that a Coris species wrasse could do well in an aquarium, it could be easily taken as an understatement. The vast majority of Rainbow wrasses can readily make the adjustment from wild reefs to captive conditions with minimal stress. Just like any other marine fish, however, the proper conditions for captive care need to be established prior to realizing success. Also, despite the success of establishing a healthy Rainbow wrasse in an aquarium, it might also turn into a traumatic experience for the aquarist. A few basic precautions will ensure that both hobbyist and fish will benefit from the relationship.

Named the Black-bar Rainbow wrasse for obvious reasons, Coris nigrotaenia is endemic to the southern stretches of the Gulf of Oman where they prefer excessive water current off of rocky points. Left (male), right, (female). Photos courtesy of John Randall.

For starters, a typical reef aquarium is likely a poor habitat for a new Coris wrasse. Well, let me rephrase that - it is likely a great place to put a Coris wrasse, but the aquarium owner will likely not enjoy the outcome. The aquarium's cleaning crew will be an excellent, much needed snack for the new wrasse to work on as it begins to settle into its new home and adjust to eating prepared foods.

The African Rainbow wrasse, Coris cuvieri, is a wide ranging and beautiful species, likely accounting for its regularity within the aquarium trade. Male (top), juvenile (bottom). Photos courtesy of John Randall.

Assuming the aquarist's intention is not to feed the new wrasse a steady diet of snails and hermit crabs, the fish will likely wind up in a non-reef aquarium, or at least one that does not contain motile invertebrates as either decorative inhabitants or as a janitorial crew. However, this natural diet of the Rainbow wrasse will need to be supplemented if its natural prey is not available. Recommended food items would include krill, mysid species shrimp, clam or mussel meat, and just about any other commercially available food designed with the carnivore in mind. A minimum of two large feedings per day should be considered for adults, with more frequent feedings for juveniles as the young, active wrasses expend a good amount of energy throughout the day.

The aquarium décor is another consideration. Rock wall designs, which feature a large portion of sandbed, will ease their adjustment to captivity. These wrasses spend the vast majority of their daylight hours roaming open water. Densely packed rockwork is not terribly important, as long as at least some suitable shelter is provided. Even so, it is unlikely to be used often, possibly more so as a hunting ground than as a hiding place. Juveniles are more likely to concern themselves with the rockwork, however, as they may not feel completely comfortable. Aquascape the aquarium accordingly, ensuring that both plenty of open sand and plenty of hiding places are available.

	The Central Pacific wrasse, Coris centralis, has been found only around the Line Islands including Washington, Fanning, and Christmas Islands. The top photo is a female, the male is in the bottom picture. Photos courtesy of John Randall.

Speaking of hiding places, the wrasse will need a sandbed several inches deep into which it can dive. This would include mostly oolitic sand without much rubble rock or crushed oyster shell. In aquariums containing a mixture of sand grain sizes and grades, the wrasse will likely do a little rearranging of its own until it has created areas of soft sand, ready for its immediate disappearance. Every night when the Rainbow wrasse retires, it dives into the sandbed, leaving no telltale signs except for a small cloud of sand dust, which quickly dissipates. It is there that it sleeps until the sun rises again, at which time it slowly rises out of the sandbed and inspects its surroundings before fully emerging. Sand sometimes sticks to its slime coat for a few minutes after waking, but will usually be blown off by water currents in short order. You can expect your Coris wrasse to go to sleep, and wake up, at nearly the same time each day. Their internal clock is amazingly predictable. At first, this might be a problem, as they will initially still be functioning on their native Indo-Pacific (or Atlantic) time. As the days and weeks pass, though, the fish will slowly readjust their schedule to more closely resemble the tank's photoperiod. Finally, larger pieces of rubble should be included as "play toys" for the fish. Chances are good that the wrasse will pick up, flip over, toss around, or even swim around with these larger pieces of rock. They will be a source of natural foods as it hunts underneath the overturned rocks, as well as seemingly using them as a toy for passing the time. Indeed, it is likely that this characteristic will also entertain the aquarist.

The size of the aquarium is a serious consideration. Many of these species become much too large for all but the biggest of home aquariums. A foot-long actively swimming and aggressively eating wrasse is nothing to be taken lightly; it needs suitably large housing. Juvenile Coris wrasses may do well in 4 - 6' long aquariums for a brief period, but if fed appropriate amounts of food, the wrasse will quickly grow into a very large fish, almost certainly requiring a 10' long aquarium as an adult so that even these smaller species can spread their "wings," or pectoral fins. Quite simply, the larger species are not suitable for home aquaria.

	The Lined Rainbow wrasse, known among ichthyologists as Coris ballieui, is an endemic of the Hawaiian Islands. The female coloration was mistakenly named C. rosea. The top photo is a male, the bottom picture is a female. Photos courtesy of John Randall.

Suitable tankmates include a lot of the larger or active fish appropriate for reef aquariums. Surgeonfish, butterflies, angelfish, Anthias and damselfish are all good options. Those fish are both active enough to compete for food and large enough to defend themselves, if needed. In most instances, however, the wrasse will not be the aggressor. It will generally mind its own business, going about its never-ending search for food. Smaller fish will be at risk of attack or harassment, though, so it may be best to avoid small gobies, flasher wrasses or dartfishes. Additionally, slow feeders may not be able to compete with the wrasse at feeding time and therefore either direct feeding will be required or the aquarist should opt to do without the reticent feeders. Finally, in regards to fish, it would likely be wise to avoid multiple Rainbow wrasses in the same aquarium. If you truly desire to the mix species, however, avoid adding two males. This combination will undoubtedly result in fierce battles among the males. The addition of two females, or one male and one female, should work in larger aquariums.

Compatibility chart for the genus Coris:

Fish	Will Co-Exist	May Co-Exist	Will Not Co-Exist	Notes
Angels, Dwarf	X			Should co-exist well. Add fish when they are nearly the same size.
Angels, Large	X			Should co-exist well. Add smaller of the two planned fish first.
Anthias	X			Should co-exist well. Add the Anthias first.
Assessors		X		Will mix but the Assessor will remain hidden for the majority of the time.
Basses	X			Should co-exist well.
Batfish	X			Should co-exist well. Batfishes in first.
Blennies	X			Should co-exist well. Blennies in first.
Boxfishes	X			Should co-exist well. Boxfishes in first.
Butterflies	X			Should co-exist well.
Cardinals	X			Should co-exist well. Cardinals in first. Cardinals may be less active than normal with the active wrasse present.
Catfish	X			Should co-exist well.
Comet	X			Should co-exist well.
Cowfish	X			Should co-exist well. Cowfish in first.
Damsels	X			Should co-exist well. Wrasse in first.
Dottybacks	X			Should co-exist well.
Dragonets	X			Should co-exist well. Consider a refugium for smaller aquariums.
Drums	X			Should co-exist well.
Eels	X			Should co-exist well.
Filefish	X			Should co-exist well.
Frogfish		X		Large frogfish can consume small wrasses.
Goatfish	X			Should co-exist well.
Gobies		X		Feeding the gobies directly will likely be necessary.
Grammas	X			Should co-exist well. Grammas in first.
Groupers	X			Should co-exist well. Add species at the same general size.
Hamlets	X			Should co-exist well.
Hawkfish	X			Should co-exist well.
Jawfish		X		Coris wrasse may hinder the natural activity of the jawfish. Add jawfish first.
Lionfish	X			Should co-exist well. Wrasse in first.
Parrotfish	X			Should co-exist well.
Pineapple Fish	X			Should co-exist well.
Pipefish			X	Pipefish require an aquarium to themselves.
Puffers	X			Should co-exist well. Puffers in first.
Rabbitfish	X			Should co-exist well.
Sand Perches	X			Should co-exist well.
Scorpionfish	X			Should co-exist well.
Seahorses			X	Seahorses do best when given their own aquarium.
Snappers	X			Should co-exist well.
Soapfishes	X			Should co-exist well. Soapfishes in first.
Soldierfish	X			Should co-exist well.
Spinecheeks	X			Should co-exist well.
Squirrelfish	X			Should co-exist well.
Surgeonfish	X			Should co-exist well.
Sweetlips	X			Should co-exist well. Add fish when generally the same size.
Tilefish		X		Tilefish in first. Natural activity may be hindered by presence of the wrasse.
Toadfish			X	Toadfish can consume small wrasses.
Triggerfish		X		The more aggressive triggerfish should be avoided. Wrasse added first.
Waspfish	X			Should co-exist well.
Wrasses		X		Avoid two male wrasses in the same aquarium.

As should be rather obvious at this point, motile invertebrates are best avoided unless you are purposely adding them as supplemental food reserves. Conversely, corals should be left alone. I say "should be" because, on occasion, the wrasse may decide to move or flip a coral over in its search for food. This is usually not cause for much concern, but in rare instances, the wrasse may actually prefer the coral to be upside-down, and thus any attempts by the hobbyist to right the coral will be answered with a prompt reversal as soon as the coast is clear. Clearly, additional measures, such as securing the coral with epoxy, will need to be taken if this happens to you.

Meet the Species

Only a handful of Coris wrasses appear with any regularity in the aquarium trade. This is probably a good thing simply because the adult size of many of these fish is more than most hobbyists bargained for or expected. Perhaps the most readily identifiable species is Coris aygula, whose availability is probably assisted by having the genus' largest wild distribution. The Twin-Spot or Clown Coris wrasse is remarkably beautiful as a juvenile, and often lures unsuspecting aquarists into purchasing it on impulse. However, the cute juvenile grows into a huge adult nearly 2' long. Rumors abound of individuals in this species reaching a length of over 3', but when several hundred of these species were collected for scientific research, the largest one speared was just under 24" (Randall, 1999). Furthermore, Randall (1999) questions the reality of any Coris that is claimed to be over 700mm (27.5 inches). Regardless, it remains among the two largest species of the genus.

The Queen of the family is Coris formosa. Plenty of confusion exists over this name, however. In his most recent revision, Randall (1999) chooses the name C. frerei at "the insistence of a colleague." After publication, however, Randall discovered his error and corrected himself in Parenti and Randall (2000). Therefore, research will likely have to incorporate both names to ensure locating all available information. General hobby literature has incorrectly stated that individuals reach up to 24"; ichthyologists, however, have recorded only a 17" individual as the largest from a sample size of 50 fish.

The final, commonly occurring Coris wrasse in captivity is C. gaimard. Adults of this species, commonly called the Yellowtail Coris wrasse, will reach 10" in length. Their size may seem to indicate that they may be a better option for home aquariums, but keep in mind that adults have been noted to consume nearly 65% of their diet in the form of snails and crabs.

Very little difference can be detected between juveniles of Coris gaimard (above) and C. cuvieri, but as adult coloration begins to unfold, the differences are clearly noted. At one point these two species were regarded as sub-species. The top right photo is a female, the male is seen to the right. Photos courtesy of John Randall.

One last word regarding Coris wrasses in regards to imposters… Many online and local retailers of marine fish have a tendency to label fish by a common name only. Without getting into a deep discussion regarding the errors involved in using common names, such a practice is typical with the Coris name. Several fish are commonly sold as the Yellow Coris wrasse or Green Coris wrasse when, in fact, these fish are not Coris wrasses whatsoever. For aquarists, the trouble arises when these fish have different captive care requirements than do the true Coris wrasses. Providing the proper living conditions begins with knowing precisely which fish you have purchased. Only then will your research be accurate and helpful. It would be wise, therefore, to use caution when shopping and seeing fish labeled as a various color of Coris wrasse.

Conclusion

Rainbow wrasses come in a variety of sizes and colors. Many choices are offered in aquarium stores, but not all of them will make the best inhabitant for your aquarium. With careful selection a hobbyist can enjoy years of success with these interesting and beautiful fish. Choosing incorrectly can, at best, lead to a fish outgrowing the aquarium and, at worst, a wrasse that causes a tremendous amount of destruction. Astute aquarists will make their choices wisely.

References:

Ayling, T. and Cox, G.J. 1982. Collins Guide to the Sea Fishes of New Zealand. 343 pp. Williams Collins Publishers Ltd., Auckland.

Baensch, H.A. 1994. Wrasses. Baensch Marine Atlas, Volume 1. Microcosm. Shelburne. 1215 pp.

Chave, E.H. and Mundy, B.C. 1994. Deep-sea benthic fish of the Hawaiian Archipelago, Cross Seamount, and Johnston Atoll. Pac. Sci. 48(4): 367-409.

Hobson, E.S. 1974. Feeding relationships of teleostean fishes on coral reefs in Kona, Hawaii. Fishery Bull. 72(4): 915-1031.

Lacepede, B.G.E. 1801. Histoire Naturelle de Poissons. Vol 3. xxvii + 55pp. Chez Plassan, Paris.

Lieske, E. and R. Myers, 1994 Collins Pocket Guide. Coral reef fishes. Indo-Pacific & Caribbean including the Red Sea. Haper Collins Publishers, 400 p.

Linnaeus, C. 1758. Systema Naturae per Regna Tria Naturae, secundum Classes, Ordines, Genera, Species cum Characteribus, Differentiis, Synonymis, Locis. 10^th Edition. Vol. 1, Regnum Animale. Ii +824pp. Holmiae (Stockholm).

Michael, S.W. 1998. Reef Fishes Volume 1. Microcosm. Shelburne. pp. 624.

Michael, S.W. 1999. Marine Fishes: 500 + Essential-To-Know Aquarium Species. Microcosm. Shelburne. pp. 448.

Parenti, P. and J.E. Randall, 2000. An annotated checklist of the species of the labroid fish families Labridae and Scaridae. Ichthyol. Bull. J.L.B. Smith Inst.Ichthyol. (68):1-97.

Randall, J.E., Allen, G.R. and Steene, R.C. 1990. Fishes of the Great Barrier Reef and Coral Sea. 507pp. Crawford House Press, Bathurst, N.S.W. and University of Hawaii Press, Honolulu.

Randall, J.E. 1999. Revision of the Indo-Pacific Labrid Fishes of the Genus Coris, with Descriptions of Five New Species. Indo-Pacific Fishes. Bern. Pau. Bis. Mus. 74pp.

Roede, M.J. 1966. Notes on the labrid fish Coris julis (Linnaeus, 1758) with emphasis on dichromatism and sex. Vie et Milieu, ser. A, 17(3): 1317-1333.

Sano, M., Shimizu, M. and Nose, Y. 1984. Food habits of teleostean reef fishes in Okinawa Island, southern Japan. Bull. Univ. Mus., Univ. Tokyo, no 25: 1-128.

Seret, B and Opic, P. 1986. Poissons de Mer de l'Quest African Tropical. Orstom, Paris. 450pp.