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Damselfishes are an extremely important group of tropical and sub-tropical marine fishes, for the wild and saltwater hobbyists. Damsels provide a vital link both as reef forage fishes as well as excellent beginner marine aquarium specimens. What makes them so great is their diversity, beauty and tolerance of chemical and physical conditions, "interesting" behavior when crowded and general compatibility with fishes and invertebrates. To top all this off damselfish species normally accept all types of food eagerly and are very disease resistant.
Amongst the premier members of the family, the damsels of the genus Dascyllus reign supreme in many ways. Some are tough beyond simple aggressiveness for their size. Though not bedecked in brilliant warm and cool colors as other damselfish genera, their simpler black and white patterns are more than made up for in hardiness and antics. Here we will cover which species are preferable, how to go about selecting the best specimens, avoiding overly agonistic behavior, and a few of my favorite biological/aquaristic insights.
Along with the clown-anemone fishes (Amphiprion) damselfishes make up the family Pomacentridae, with some 25 genera and 320 species.
According to Dr. Gerald Allen, the foremost authority on the systematics of the group, the genera Acanthochromis, Chromis and Dascyllus should be placed together in a subfamily, the Chrominae on the basis of shared structural characteristics (see Allen, 1975, p.34).
Of the nine described Dascyllus species three are "fixtures" in the aquarium hobby; the Three-Spot or Domino, Dascyllus trimaculatus, Four-Striped or Blacktail Humbug, Dascyllus melanurus, and the Three-Striped or White-Tailed Damsel, Dascyllus aruanus. Every seasoned marine aquarist has seen and used these for testing, breaking in nutrient cycling, ditherfish and general amusement.
Of similar appearance to the three-spot and unfortunately, temperament, is the Hawaiian endemic, Dascyllus albisella. More striking as a juvenile, with darker black and a bolder, larger triangular body spot, the Hawaiian is no match for the domino in sturdiness. I'd suggest Dascyllus albisella only for a biotopic, or serious study set-up.
The blue-spotted Dascyllus carneus and aptly named reticulated Dascyllus reticulatus are occasionally offered in the trade in the west, and tend to be of irregular touchiness. I've seen whole shipments "crash" without probable cause. Much better are the three "standards" listed above.
Not to leave them out without mention, Marginated Dascyllus marginata, and Strasburg's Dascyllus, Dascyllus strasburgi are rarely found in the trade other than as specialty orders (Strasburg's is from the Marquesas, marginates from the Red Sea), "contaminants" or "mixed" in assorted damsel shipments. My limited experience, first and second hand, with these other Dascyllus places them in the same aquarium-useful box as the Dascyllus carneus and reticulatus; that is, not very.
Dascyllus species are confined to the tropical Indo-West Pacific overall; shallow reef areas are typical habitat, always near close cover.
Size: How big have you seen these fishes? Three and Four Stripes attain a good four inches (10 cm.), the Domino and Hawaiian can reach half a foot.
On any given day the three principal species are readily available from dealers. Mixtures of Three-Spots or Dominoes (Dascyllus trimaculatus, three and Four Stripes or Humbugs (D. aruanus, D. melanurus) Yellow-Tail Blue and Blue Damsels (Chromis cyaneus et al.) various Chromis, Beau Gregorys, Sergeant Majors (Abudefduf species), so-called "deep water" damsels (Glyphidodontops species et al) among others are variously offered as the lowly low-end miscellaneous damsels.
The following criteria for picking out healthy Dascyllus apply to all marine fishes, but in particular the damsels:
1) Buy from a healthy system; one with no dead or dying specimens. The majority of losses of these fishes are due to either shipping problems, or poor stock management. Look for signs of gill burn/ammonia poisoning from recent shipping; cut-marks on damsels from mis-handling and aggression and avoid that tank.
2) Beware of behavior problems; of tanks of damsels with individuals hanging, drifting around having "private meetings". or a set-up with one alpha damsel beating all else senseless.
3) Don't buy the smallest (less than 1/2 inch) or the largest (as a rule, more than two inches long) individuals available. Small ones die too easily and large ones don't adapt well to captive conditions.
4) Buy and introduce your damsels all about the same size; this reduces inter and intra-species aggression.
5) Buy stock that have acclimated-stabilized. The "top three" Dascyllus damsels that have been adequately acclimated and held for just a week or two are extremely hardy; one's that are shipping-stressed ofttimes perish mysteriously.
Dascyllus damsels are easy to keep in aquaria; they are not fussy in terms of water chemistry and physics.
Any amount of light, dim to bright, will be okay. Natural or synthetic water makes no difference in terms of vitality or reproduction in captivity. A pH of 8.0 to 8.3 is favored; no ammonia, nitrite and as low a concentration of nitrates as practicalis the rule as with most marines.
Though dealers purposely overcrowd their systems, this should be avoided; grant your Dascyllus five to ten gallons of water each at a minimum for small to adult sizes.
Dascyllus, like other small marines must have hiding spaces. Provide coral, shells, plants- some nooks and crannies for social-psychological shelter.
Are you aware that small damsels are a dietary mainstay for most fishes whose mouths are large enough to accommodate them? You will be if you don't measure those would-be predators before introduction.
Not to simply state that Dascyllus are pushovers however; anyone who has not been challenged, indeed bitten by these mighty mites, has not had their hand in their tank or been diving in their waters. Dascyllus can/will hold their own with any organism not big and fast enough to engulf them.
Acclimation:At the very least a simple freshwater dip/bath, with or without other additions ought to be employed in transferring Dascyllus from your supplier to their new home. More ideal is an intermediate stay in a quarantine/hospital tank for "hardening" and ensuring the elimination of pests and parasites.
Foods/Feeding/Nutrition:Dascyllus damsels are dominantly planktivorous in the wild, eating water-borne zooplankters, secondarily feeding on benthic algae. In captivity they accept all foods greedily. In fact, you may have to actually "beat them with a stick" to allow less robust feeders a chance at the table.
Frequent, small feedings of a variety of foods (dry, frozen, fresh, & live; both vegetable and animal) will help settle in the stock and reduce aggressive turmoil.
Infectious and Parasitic Disease:
Dascyllus are parasitized internally and externally by several species of sporozoans, Cryptocaryon, Oodinium, roundworms, flukes tapeworms and crustaceans. For the most part they're disease resistant and coupling preventative measures with good environments generally results in good health.
External infections can be excluded or treated by freshwater dips or lowered specific gravity. These damselfishes respond well to prophylactic copper treatments.
Territoriality can be a type of social disease. Keep your powers of observation sharp for extreme interactions and remove bullies. Inter-specific aggression is probably the single largest source of damselfish mortality, especially with Dascyllus, in particular that domineering domino, D. trimaculatus.
Sex and the Single Dascyllus
Dascyllus are substrate spawners ala neotropical Central American cichlids. Pairs lay their several hundred sticky eggs on dead coral or other hard material they've cleared, where they are guarded VIGOROUSLY by the male until hatching, usually in three days. Difficulties in captive reproduction arise in getting sufficient food to the pelagic young.
Other Biology of Note:
Geez, how much time/space do we have? Chemical and sound communication (yes, they're noisy) may be explored in a literature search and in your own tanks.
How long do they live? Dascyllus damsels have been kept in captivity for more than ten years.
Young to moderate size D. trimaculatus and the Hawaiian sibling species D. albisella are frequently found in the same sort of mutualistic symbiotic relationship as Clownfishes; cavorting in and amongst sea anemone tentacles. Sometimes right along with Amphiprion species!
The three principal species of Dascyllus used in the hobby, the three-spot, three and four stripe, have proven to be indispensable to saltwater aquarists. What more could you ask for? Their inexpensive, amongst the hardiest of marines, accepting of the widest range of conditions, and eat like no tomorrow.
Do you have a friend who's considering a salt set-up? Do direct them to these damsels definitely not in distress, the top three Dascyllus.
Allen, Gerald R. 1975. Damselfishes of the South Seas. T.F.H., Neptune City, N.J.
Allen, Gerald R., 1991. Damselfish of the World. Aquarium Systems, OH.
American Society of Ichthyologists and Herpetologists, 1978. The Biology of the Damselfishes a symposium held during the 56th annual meeting of the ASIH. Rosentiel School of Mar. & Atm. Sci. U. of Miami, 1980, 145-328.
Burgess, Warren E., 1979. The genus Dascyllus. TFH 5/79.
Burgess, Warren E., Herbert R. Axelrod & Raymond E. Hunziker III, 1990. Atlas of Aquarium Fishes, v. 1, Marine Fishes. T.F.H. Publications, NJ.
Emmens, C.W., 1984. Damselfishes. TFH 9/84.
Fenner, Bob. Successfully selling the popular marines. PSM 1/89.
Fenner, Bob & Cindi Camp, 1991. Damselfishes, saltwater bread and butter. FAMA 10/91.
Flood, A. Colin, 1992. Those darling damsels. TFH 8/92.
Pyle, Richard L. & Lisa A. Privitera, 1990. The black and gold Dascyllus, Dascyllus trimaculatus (var.) (Ruppell). FAMA 2/90.
Randall, H.A. & G.R. Allen, 1977. A revision of the damselfish genus Dascyllus (Pomacentridae) with the description of a new species. Records of The Australian Museum. 31(9): 349-385.