Combtooth Blennies: Bewitching Bottom DwellersAuthor: Jeff Kurtz
The group of fishes collectively known as the blennies is far too vast and diverse in behavior and morphology to discuss in general terms within the confines of a single “Salt Creep” installment. To put the size of this group into perspective, consider that there are six families of blennies, consisting of 127 genera and 732 species. However, one particular group of blennies, the combtooths, family Blenniidae, includes several species that are really worth their salt in the marine aquarium and, fortunately for hobbyists, are also commonly available in the marine aquarium trade.
So named for their comb-like dentition, which they use to scrape algae from the rocks and other hard substrates, the combtooth blennies are, to many hobbyists, the archetypal blennies. Most exhibit the characteristic scale-less, elongated, almost eel-like body; continuous, flowing dorsal and anal fins; a pronouncedly blunt head; high-set, bulbous eyes; comically prominent lips; and curious tentacle-like appendages called cirri, located between the eyes. Not the most elegant look, to be sure, but these blennies are really loaded with character and personality. And, as I’ll describe ahead, at least one of the combtooth blennies is especially prized by reefkeeping hobbyists for helping to keep troublesome algae in check.
Most species lack a swim bladder as adults, so the blennies are typically bottom-dwellers, hopping from rock to rock as they forage. This behavior brought about the common name “rock skipper,” which is loosely applied to more than one species. If you should happen upon a specimen generically labeled “rock skipper blenny” at your local aquarium dealer, be sure to ascertain the species—and research it—before buying. This is an especially important consideration if you plan to introduce the specimen to a reef aquarium, as some blennies are inclined to nip at corals and other sessile invertebrates while others can generally be considered reef safe. Also, some species are collected from cooler waters and are completely unsuitable for the tropical marine aquarium. You might see similar casual use of the name “scooter blenny” to label various species. Again, be sure you know which species you’re dealing with before committing to buy.
At first glance, it’s easy to mistake blennies for members of another enormous assemblage of bottom-dwelling fish, the gobies. However, there are some tell-tale signs that hobbyists can look for to help distinguish between members of the two different groups. For example, gobies typically have two distinct dorsal fins while blennies (with exceptions, of course) have one long continuous dorsal fin. The aforementioned cirri can also be a distinguishing characteristic, as they are not present on gobies. In addition, the pelvic fins of many gobies are fused together. In some species, the fins are fused to the extent that they form a suction disc, which helps secure the fish to its rocky purchase on the reef. However, one could argue that fused pelvic fins are not necessarily easy to spot while looking over a specimen that is resting on the bottom of a tank at your local aquarium store.
The combtooth blennies offer the advantage of reaching a manageable adult size of 3 to 5 inches (depending on the species), which makes them good candidates for the “average home aquarium,” which I consider to be in the range of 20 to 55 gallons. In fact, most will do just fine if housed in a 20- to 30-gallon system. Just be sure to provide ample rockwork with numerous bolt holes and hiding places for your blenny to hide in and gain a sense of security.
Given their ungainly looks and bottom-dwelling tendencies, you might be tempted to think that blennies aren’t good jumpers. But don’t be fooled! Many a blenny has met a dusty end on the fishroom floor because its owner underestimated its leaping ability. A tight-fitting glass or acrylic aquarium cover is a must for keeping blennies properly contained.
As I alluded to earlier, many of these blennies, with their comb-like teeth, are adapted to grazing on microalgae. Hence, they do best in a system that offers an abundant and consistent crop of algae to munch upon. If you’re an aquarist who demands a perfectly pristine, “sterile” aquarium with all surfaces clean of algae, the combtooth blennies might not be the best choice for you. Many will learn to accept substitute food offerings, such as frozen or dried herbivore formulations, but they may fail to thrive in the absence of algae to forage upon.
I should point out that there are also carnivores and omnivores among the combtooth blennies. One notable example, which I’ll describe in greater detail below, is the Midas blenny Ecsenius midas, which feeds on zooplankton in nature and therefore can be conditioned to accept mysid shrimp, brine shrimp, finely chopped seafoods, and frozen formulations.
Among the combtooth blenny “no-nos” is the beautiful leopard blenny, a.k.a. the honeycomb blenny Exallias brevis. Why dealers continue to offer this obligate corallivore (i.e., eats only coral polyps) to unsuspecting hobbyists is beyond my comprehension, but I would urge you to pass this species by if you should happen upon it for sale. Lacking its natural diet of stony coral polyps, E. brevis starves to death in captivity because it will not learn to accept substitute aquarium fare. I would urge you not to support the collection of this doomed-in-captivity species by plunking down your dollars to buy one.
Though some species are more peaceful toward their tankmates than others, territoriality can be an issue with the combtooth blennies. And results may vary! One specimen may be well behaved while another may continually cop an attitude toward tankmates. As a general rule, keep one specimen to a tank to avoid intraspecific squabbles. Similar-looking species and/or species that occupy the same niche in the aquarium, such as hawkfish, gobies, and dragonets, may also be targets of aggression. Larger tanks with abundant rockwork tend to help minimize aggression. Also, introducing your blenny and any potential rivals to the aquarium simultaneously can help reduce battling, since no specimen will have a home-field advantage.
Which of the combtooth blennies can be recommended for the average home aquarium? Actually, there are several, but what follows is my short list of noteworthy species (in no particular order) that should thrive in a system containing sufficient algae for grazing.
At the beginning of this column, I mentioned a blenny that is prized by reef aquarists for helping to keep algae in control. That prized species is the lawnmower blenny Salarias fasciatus, known also as the jeweled rockskipper, among other names. Reaching approximately 5 inches in length, this Indo-Pacific species can practically “disappear” against a background of heavily encrusted live rock, as it sports mottled white, gray, and green coloration disrupted by dusky bands and dark streaks.
A note of caution: like many “utility” species, S. fasciatus can eat itself out of house and home and eventually starve if an ample, regenerating crop of algae is not present. This can lead to something of a paradox for those reefkeepers who are intolerant of any algal growth. In addition to algae growing in the tank, be sure to offer a variety of plant-based foods, such as spirulina, dried marine algae, and frozen herbivore formulations.
Also, be aware that some specimens sold under the name “lawnmower blenny” may be a different species, which may or may not be suitable for reef systems. Ask for this fish by its scientific name!
Hailing from the tropical western Atlantic, the red-lip blenny Ophioblennius atlanticus also approaches 5 inches in length. Its overall coloration is a fairly unspectacular reddish brown (sometimes a pinkish gray), but its red lips, which create the impression that this fish is wearing lipstick, give the species a slightly comical aspect. O. atlanticus is generally considered reef safe but has been known to nip at corals and the mantles of Tridacna clams. Feed as described above for S. fasciatus.
As mentioned earlier, the Midas blenny Ecsenius midas differs from most of the combtooth blennies in that it eats zooplankton rather than algae. This blenny is named for its brilliant orange-yellow color phase, which allows this Indo-Pacific species to school with the similarly colored Pseudanthias squamipinnis, another planktivore. Fishbase.org reports that this species, which reaches approximately 4 inches in adult length, is able to change color rapidly when leaving the bottom to school with other fishes in open water.
E. midas will learn to accept a variety of plankton-like foods in the aquarium, such as mysid shrimp, vitamin-enriched brine shrimp, and frozen formulations. As with most planktivores kept in the confines of an aquarium, it’s preferable to offer several smaller feedings per day rather than one large feeding.
Similar in adult length to E. midas (approximately 4 inches), the bicolor blenny Ecsenius bicolor, another Indo-Pacific species, is a perennial hobbyist favorite for its subtle good looks—a dark brown anterior giving way to a yellow posterior (other color phases occur, as well)—and general ease of care. E. bicolor is usually well behaved in the mini-reef, though some specimens have been known to sample or nip at corals and other reef invertebrates. Offering a varied diet of plant-based foods as you would to the other algae-grazing species described above will keep this delightful species in optimum health.
Fenner, R. M. 2001. The Conscientious Marine Aquarist. TFH/Microcosm Professional Series, Neptune City, NJ.
Fishbase.org (www.fishbase.org)Nilsen, A. J., Fossa, S. A. 2002. Reef Secrets. TFH/Microcosm Professional Series, Neptune City, NJ.