Much attention has been given to captively breeding marine fish, and deservedly so. As a dedicated, conscientious, and concerned hobbyist I am always trying to lessen my negative impact on the natural reef, and I also feel this practice should be undertaken by hobbyists worldwide. The Apogonidae is one fish family that lends itself well to this endeavor. Much of the attention the marine aquarium trade has directed at members of this family has been focused Pterapogon kauderni. That sounds like a good enough reason for me not to discuss that genus or species in this column. Instead, I'll concentrate my attention on the genus Cheilodipterus, more commonly known as the Lined Cardinalfish or Big-toothed Cardinals.

Meet the Family

Cardinalfish are divided into two families. I will not discuss Epigonidae, as members of that family are unlikely to be available in the marine trade. The Lined Cardinalfish, however, are in one of 27 genera containing over 250 species which comprise Apogonidae, the second Cardinalfish family. Furthermore, the Lined Cardinals are classified in the subfamily Apogoninae.

When Lacepede (1801) grouped together nine similar Apogonidae he introduced the world to the genus Cheilodipterus. He named two additional Apogonids, and placed them into the genus Centropomus. Not until Cuvier (1828) reexamined these two species were they assigned to Cheilodipterus. This remained the status quo until Bleeker (1863, 1874) decided it was time to shake things up a bit. In essence, he succeeded only in confusing the diagnostics of the family hierarchy. Among his many errors was deeming Cheilodipterus as an invalid genus and replacing it with Paramia. Although Lachner (1953) and Fowler and Bean (1930) agreed, Schultz (1940) and Fraser (1935) correctly pointed out that Paramia should be a junior synonym of Cheilodipterus. In addition to discounting the notion of replacing Cheilodipterus with Paramia, Schultz (1940) was confident that Cheilodipterus should be divided into four genera, including the newly named Cheilodipterops and Jadamga, and raising the subgenus Desmoamia named by Fowler and Bean (1930) to generic status. Besides agreeing with Bleeker (1863, 1874), Lachner (1953) discounted the four genera classification of Schultz (1940). Finally, in addition to moving Cheilodipterus polyacanthus to the new genus Coranthus, Smith (1961) erected the sub-family Cheilodipterinae for species with the following identifying features: caniniform teeth, ctenoid scales, and a serrated preopercular edge. Genera placed into this newly erected subfamily are Cheilodipterus, Paramia, and Coranthus. This work was invalidated with the conclusion of Fraser's (1972) extensive osteological study. The features set forth by Lacepede that were first used for identifying species for this genus, which included thick and sharply-pointed lips, opercles without denticles, and two dorsal fins, were accurate enough to withstand the scrutinizing research. Cheilodipterus species were therefore re-assigned to the subfamily Apogoninae. In the most recent revision of the genus, Gon (1993) follows the classification of Fraser (1972) and also adds five more species for a total of 16.

Additional identifying features found among Cheilodipterus are nine to ten dorsal rays, eight or nine anal rays, ten to 15 pectoral rays, a complete lateral line, and small conical teeth with at least a few enlarged or canine teeth.

In the Wild

Although numerous Cardinalfish genera are represented in the Caribbean, no Cheilodipterus species are present there. All species in this genus are located in the Indo-Pacific Oceans. Two species, Cheilodipterus quinquelineatus and C. macrodon, closely mirror each other in sharing the largest distribution. Cheilodipterus quinquelineatus edges just slightly further east into the Ducie Islands. Otherwise, these two species are found sympatrically. Both extend into southern Japanese waters, further north than any other Cheilodipterus and both are found in the Red Sea and along the east African coastline. Extensive collections of both species have been noted throughout Indonesia and the South Pacific as well. Finally, no Cheilodipterus species are found further south than our wide-ranging pair. The Lord Howe Islands appear to hold a decent population of each species.

In contrast, Cheilodipterus alleni has been collected only from the hot spot of coral reef animals, the region bounded by Papua New Guinea, Borneo, and Indonesia. Known only from the Persian Gulf, C. persicus is perhaps the most geographically limited Cheilodipterus species, rivaled only by C. lachneri which has not been collected outside of the Red Sea. One final note regarding distribution: no species of Cheilodipterus has been reported from the Hawaiian Islands.

Flashing a mouth full of teeth is Cheilodipterus persicus, the Persian Cardialfish. As one may expect, it is only known from the Persian Gulf. Photo courtesy of John Randall.

Cardinalfish prefer still waters over current-rich waters with excessive fish activity. This means you'll be hard pressed to find Cardinals along the reef crest, but they should be plentiful back in lagoons and sheltered reef habitats. On the rare instances where individuals of Cheilodipterus species are located on the outer reef walls and drop-offs, they almost always associate with caves or overhangs. Cheilodipterus macrodon is perhaps the only species living in such conditions with any regularity.

Cardinalfish are notoriously poor swimmers, and when that is considered in conjunction with their absence of any natural defense, it's easily understood why they try to maintain low profiles. In addition to their low-key persona, and if their large eyes didn't already tell the story, the vast majority of Cardinalfish are nocturnal. Cheilodipterus species are no different, with only three species known to make their presence well known in open water during daylight hours. Species which are noted to venture out of protected caves and lagoons during the daylight photoperiod partake in a relationship known as Batesian mimicry. Cheilodipterus parazonatus, C. zonatus, and C. nigrotaeniatus have all been recognized as Batesian mimics of Fang Tooth Blennies. Cheilodipterus parazontus is reportedly rather comfortable in open water, wearing a near-perfect costume of Meiacanthus vittatus. Cheilodipterus zonatus appears to mimic M. geminatus, and C. nigrotaeniatus mimics M. grammistes.

Despite preferring reef habitats not lit by direct sunlight, the fine-toothed Cardinalfish seek shallow areas. Several species (C. zonatus, C. parazonatus, C. novemstriatus, and C. artus) prefer the 10-20 foot depth range. Only a few species (e.g., C. macrodon, C. quinquelineatus) have been located below 100 feet. Additionally, it isn't only a peaceful overhang for which they search. Overhangs created by dense thickets of Acropora species are prime real estate and can often harbor up to 20 or more individuals, especially C. artus and C. isostigmus. On the other hand, congregations of over 20 individual C. novemstriatus have been noted to subsist among the sharp protective spines of Diadema urchins. Cheilodipterus quinquelineatus has been noted to prefer only Diadema setosum if the fish does not opt for areas of dense Acropora growths. Juveniles of C. quinquelineatus settle along reef flats until they are able to align themselves among the adults which have already staked out the prime locations.

Feeding is primarily done in the evening hours, although they will eat any time they are given the chance. In addition to the three species that are diurnal, the remainder will move from the patch reefs and out over reef flats to feed. Without the protection the reef offers, Striped Cardinalfish are at their most vulnerable at this time. Make no mistake about it, these Cardinalfish are active predators. They have a mouth full of teeth for a reason and it isn't to consume algae. Small fishes and shrimp will account for the majority of their diet while gastropods and other foods will be consumed if the situation presents itself.

In an effort to help ensure the survival of their species, all Apogonidae are mouth brooders, meaning the adult fish incubate their eggs in their mouth. In the case of Cardinalfish it is the male that carries the eggs for the full incubation term, starving himself of food throughout this entire time. The female is then able to consume food for the energy required to produce another batch of eggs.

The Artus Cardinal, Cheilodipterus artus, prefers thickets of Acropora to hover in between. It's large size (for a Cardinalfish), five inches of total length, dictates for a discretionary tankmate list. Photo courtesy of John Randall.

In the Home Aquarium

Striped Cardinalfish are hardy aquarium inhabitants. Just as any fish does, they do require some basic accommodations to ensure long-term survival. For many marine aquarium fish, aquarium size is a valid concern. This isn't the case with most Cardinalfish. Their small size coupled with their lack of activity and defended territory allows for the use of smaller aquariums. The smallest Fanged Cardinalfish, C. pygmaios, tops out at a maximum of three inches, but realistically may never reach more than two inches. The majority remain a size similar to this or may extend up to four inches. The exception, C. macrodon, can reach up to ten inches. Obviously, in this case, a small aquarium will not be appropriate. However, for any of the fish that remain under four inches an industry standard 30-gallon aquarium should be suitable. Cheilodipterus macrodon would do well in aquariums four feet long or larger. Additionally, provide all Cardinalfish with enough live rock arranged in such a manner that it creates many overhangs and caves. Areas of little to no light will be utilized, especially upon the fishes' initial introduction to the aquarium.

As the name may suggest, Cheilodipterus pygmaios is the smallest of all Lined Cardinals. Known only from the Red Sea, it is an uncommon import. Photo courtesy of John Randall.

Generally, my recommendation would be to maintain these fish as pairs and not harems. This is because pairs have a tendency to become defensive during spawning periods. On occasion, however, these fish are noted to congregate in harems. Attempting to elicit this same behavior in a home aquarium will require a considerably larger aquarium. Additionally, hiding places need to be more numerous. It would be wise to start with all juvenile fish as adults are unlikely to mix well upon introduction, whereas juveniles prefer safety in numbers. As they age and pair off, however, they may need to be removed to separate aquariums.

Besides co-existing with themselves, Fanged Cardinals will do well with a large assortment of the usual aquarium fish. Due to their shy tendencies, they will generally ignore any fish they are unable to eat. The exception to this is a spawning pair, which will defend themselves as needed. Even then, the aggressive nature is only defensive posturing and quick, short strikes which typically result in no damage. On the other hand, aggressive or fast-swimming fish have a propensity to cause further timidity in the Cardinalfish. Viewing opportunities will likely be greatly reduced with the introduction of fishes such as Surgeonfish, large Angelfish, or large Wrasses. Conversely, small gobies such as the non-cleaning species of Gobiosoma may be in danger of being consumed. As a general rule, if a fish can fit into a predator's mouth, there is a definite chance that it eventually will.

Compatibility chart for Cheilodipterus species:

Fish	Will Co-Exist	May Co-Exist	Will Not Co-Exist	Notes
Angels, Dwarf	X			Should be peaceful tankmates.
Angels, Large	X			Should be peaceful tankmates.
Anthias	X			Should be peaceful tankmates.
Assessors		X		Avoid mixing large Cardinalfish with Assessors.
Basses	X			Should be peaceful tankmates.
Batfish	X			Should be peaceful tankmates.
Blennies	X			Should be peaceful tankmates.
Boxfishes	X			Should be peaceful tankmates.
Butterflies	X			Should be peaceful tankmates.
Cardinals		X		Only mix paired conspecifics.
Catfish	X			Should be peaceful tankmates.
Comet	X			Should be peaceful tankmates.
Cowfish	X			Should be peaceful tankmates.
Damsels	X			Should be peaceful tankmates.
Dottybacks	X			Should be peaceful tankmates.
Dragonets	X			Should be peaceful tankmates.
Drums	X			Should be peaceful tankmates.
Eels		X		Large, predatory eels should be avoided.
Filefish	X			Should be peaceful tankmates.
Frogfish			X	Will likely consume Cardinalfish.
Goatfish	X			Should be peaceful tankmates.
Gobies		X		Large Cardinals may prey upon gobies.
Grammas	X			Should be peaceful tankmates.
Groupers			X	Will likely consume Cardinalfish.
Hamlets		X		Large Hamlets may prey upon juvenile Cardinalfish.
Hawkfish	X			Should be peaceful tankmates.
Jawfish	X			Should be peaceful tankmates.
Lionfish			X	Will likely consume Cardinalfish.
Parrotfish	X			Should be peaceful tankmates.
Pineapple Fish	X			Should be peaceful tankmates.
Pipefish			X	Pipefish are best kept in dedicated aquariums.
Puffers	X			Should be peaceful tankmates.
Rabbitfish	X			Should be peaceful tankmates.
Sand Perches		X		Avoid mixing large Sand Perches with juvenile Cardinalfish.
Scorpionfish			X	Will likely consume Cardinalfish.
Seahorses			X	Seahorses are best kept in dedicated aquariums.
Snappers			X	Will likely consume Cardinalfish.
Soapfishes			X	Will likely consume Cardinalfish.
Soldierfish			X	Will likely consume Cardinalfish.
Spinecheeks	X			Should be peaceful tankmates.
Squirrelfish	X			Should be peaceful tankmates.
Surgeonfish	X			Should be peaceful tankmates.
Sweetlips			X	Will likely consume Cardinalfish.
Tilefish	X			Should be peaceful tankmates.
Toadfish			X	Will likely consume Cardinalfish.
Triggerfish		X		Some Triggerfish require a tank to themselves.
Waspfish	X			Should be peaceful tankmates.
Wrasses	X			Should be peaceful tankmates.

Note: While many of the fish listed are good tank mates for Cheilodipterus species, you should research each fish individually before adding it to your aquarium. Some of the mentioned fish are better left in the ocean or for advanced aquarists.

Invertebrates are another concern. Sessile invertebrates pose little risk to Cardinalfish, and in return Cardinalfish will not be a threat of any type to sessile invertebrates. Even most motile invertebrates occupying the same aquarium will have free range of the real estate. The temptation with small ornamental shrimp, however, is too great to resist. As an integral part of the Fanged-Cardinalfishes' natural diet, these delicate crustaceans have little chance of making it through even a single evening.

Assuming you are not planning to feed your Cardinalfish a steady diet of decorative shrimp and fish, you will need to find suitable substitutes. Good food options to offer are most any foods designed for carnivorous fish. Items such as mysid shrimp are an excellent choice, while the fish will also appreciate enriched brine shrimp. The larger species of Cheilodipterus, such as C. macrodon, will require food of more substance. Frozen/thawed krill and silversides are the best options in this instance, but most any food for larger carnivores will be a good match. Getting newcomers to eat may present a problem initially, but it's easily overcome by using live foods. Live brine shrimp should work with the smaller species, but the larger species may require feeder shrimp. If this is the scenario you are following, try mixing in prepared foods during the feedings, gradually reducing the amount of live food until you have eliminated it completely. Finally, try feeding with the lights off. When newly introduced nocturnal fish are stressed, they will become less stressed during the evening hours long before they begin to settle into the daylight photoperiod. An actinic photoperiod will enhance the aquarist's enjoyment, as it will likely facilitate more opportunities for viewing earlier in the husbandry of the fish. Additionally, moonlights would be an ideal way to enable the aquarist to watch the Cardinalfishes' nighttime antics. To catch a glimpse of their natural instincts, drop a couple of small, live freshwater feeder shrimp, commonly called Ghost Shrimp, into the tank in the middle of the evening while viewing with moonlights.

An interesting aspect of maintaining certain Cheilodipterus species is the opportunity to witness two types of symbiotic relationships. By maintaining either C. novemstriatus or C. quinquelineatus with Diadema setosum, you'll have the opportunity to watch commensalism: the relationship which benefits one species but not the other. In this instance, it is obviously the Cardinalfish that gains the benefit of protection from predators within the spines of the urchin. Second, maintaining C. parazonatus, C. zonatus, or C. nigrotaeniatus along with their fang-toothed blenny "stunt double" will result in Batesian mimicry: one species gains protection by associating with or imitating a second species that is less desirable to predators. In the case of the Cardinalfish it is both the association with, and similar color pattern to, the poisonous, fang-toothed blenny that gives the cardinal a hall pass on the reef crests.

Meet the Species

The most common species to appear in the aquarium trade is undoubtedly C. quinquelineatus, the Five-lined Cardinal. This shouldn't be surprising, since it enjoys the broadest distribution. Maximum size is roughly four inches, making it a mid-sized Cardinal. Keep this in mind when adding smaller fish. Sexual maturity is attained at two inches of length. The five stripes that their common name and specific epithet allude to do not develop until the fish is an adult. As a juvenile it will bear no stripes at all.

The broad distribution of C. macrodon, the Large-toothed Cardinal, assures that it will occasionally appear in the aquarium hobby. It is the largest species in the genus, reaching up to 10" of total length. As such, care should be taken when deciding on its potential tankmates. Only large predators should be considered.

The Mimic Cardinal, C. parazonatus, makes a wonderful aquarium inhabitant when it can be acquired. It is a smaller Cardinal, barely reaching three inches, making it suitable for some reef aquariums. Sexual maturity is about half the length of full-grown adults, or 1.5 inches. When kept with the Fang-toothed blenny, Meiacanthus vittatus, it makes an interesting display.

Cheilodipterus singapurensis is one of the larger Lined Cardinalfish. Also called the Singapore Cardinal, lengths of up to seven inches can be expected. Plan the tankmates accordingly. Do not keep these fish in groups as they are found as solitary fish in the wild. The reason why this genus has been given the name Fanged Cardinalfish should be evident after viewing this photo. Make no mistake; they are predators. Photo courtesy of John Randall.

Conclusion

Perhaps the only drawback to maintaining Lined Cardinalfish is their propensity to eat small fish or shrimp. That certainly restricts them from a lot of aquariums. The many benefits these Cardinals have in their favor, however, may tempt many aquarists to set up an aquarium with its overall design shaped around these fish. Being small fish not requiring large aquariums, being good eaters, displaying two different types of mimicry, readily spawning in captivity, and simply being uncommon in the trade all make these Cardinals desirable. Finally, I don't know about you, but the stressed-out look of their cousin Pterapogon kauderni really begins to get on my nerves after awhile. I don't feel the urge to make Cheilodipterus species blink nearly as strongly as I do with the Banggai Cardinal.

References:

DeLoach, N. 1999. Reef Fish Behavior. New World Publications. Jacksonville. 259 p.

Fowler, H.W. and Bean, B.A. 1930. Contribution to the biology of the Phillipine Archipelago and adjacent regions. The fishes of the families Amiidae, Chandidae, Duleidae, and Serranidae,…in the Philippine Islands and adjacent seas. Bull. W.S. Natl. Mus. 100. 10: ix + 334.

Fraser, T.H. 1972. Comparative osteology of the shallow water cardinalfishes (Perciformes: Apogonidae) with reference to the systematics and evolution of the family. Ichthy. Bull. J.L.B. Smith Inst. Ichthy. (34): v + 105.

Gon, O. 1993. Revision of the Cardinalfish Genus Cheilodipterus (Perciformes: Apongonidae), with description of five new species. Bern. Pau. Bish. Mus. No. 22., 59 pp.

Lachner, E.A. 1953. Family Apogonidae: Cardinalfishes, pp.412-498, in L.P. Schultz et al. (eds.), Fishes of the Marshall and Marianas Islands. Smithsonian Institution, Washington, D.C. 1. 685pp.

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

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

Michael, S.W. 2004. Reef Fishes Volume 2. Basslets, Dottybacks, and Hawkfishes. T.F.H. Publications. Neptune City. 296 p.

Schultz, L.P. 1940. Two new genera and three new species of cheilodipterid fishes, with notes on the other genera of the family. Proc. U.S. Natl. Mus. 88(3085):403-423.