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Pomacentrus violascens


 Pomacentrus violascens

Damselfishes are an extremely important group of ubiquitous, circumtropical coral reef fishes. Along with the clown-anemone fishes (Amphiprion, Premnas)damselfishes make up the family Pomacentridae, with some 28 genera and @ 321 species. We will discuss the anenomefishes (Subfamily Amphiprionae) in a following article.

Damselfishes (Subfamily Chrominae) provide a vital link both as reef forage fishes as well as excellent beginner marine aquarium specimens. Their extensive use is well-warranted considering their diversity, beauty and tolerance of chemical and physical conditions, gregariousness when crowded and general compatibility with fishes and invertebrates. Most damselfish species accept all types of food eagerly and are very disease resistant.

Classification:

The family's taxonomy in currently poorly known, and a wide open field with species "groups" blending/grading between different island groups. On the higher taxonomic plane, pomacentrids are closely related to cichlids which they resemble in structure, form and behavior. Both families are in the same Sub-Order of the largest Order of fishes, the Perciformes. These two families are notable within the group for being the only two families with only one pair of nostrils (nares) in most species.

Damselfishes are generally small with some species, the California garibaldi (Hypsypops rubicunda) and the giant Cortez damsel (Microspathodon dorsalis) reaching about a foot in length. Many are brilliantly hued in blues, greens, violets, reds and browns; several appear metallic. Quite a few damsels are or become drab brown or olive in later life and there are sometimes striking color and structural differences between the sexes.

Selection:

On any given day a handful or two of species are readily available from dealers. This mix generally includes Three-Spots or Dominoes (Dascyllus trimaculatus, Three and Four Stripes or Humbugs (Dascyllus aruanus et al.) Yellow-Tail Blue and Blue Damsels (Chromis cyaneus et al.) various chromis, "Beau" Damsels (Stegastes spp.), Sargent Majors (Abudefduf species), so-called "Deep Water" Damsels (Glyphidodontops species et al) among others.

As with many cichlid species, the following generalities exist when picking out damsels:

1) Buy from reputable dealers; ones who earn your trust, that feed, care for their stock and your business.

2) Buy from systems with no dead or dying specimens. Look for signs of gill burn/ammonia poisoning from recent shipping; cut-marks on damsels from mis-handling and aggression, and avoid that tank. Beware of tanks of damsels with individuals hanging, drifting around having "private meetings".

3) Don't buy the smallest (less than 2 cm.) or the largest individuals available. Small ones die easily and large ones don't adapt well behaviorally to captive conditions.

4) Buy them all about the same size; this reduces inter- and intra-species aggression.

5) Buy stock that have acclimated-stabilized. Damsels that have been adequately acclimated and held for just a day or two are extremely hardy; just-new ones may die easily.

Environment:

Damselfishes are easy to keep in aquaria; they are not fussy in terms of water chemistry and physics. Temperatures in the low to upper 70's degree F. (72-78) are ideal. Most tolerate and enjoy a wide range of salinities. The industry usually keeps theirs in a specific gravity of @ 1.017-1.018 to decrease salt mix costs, increase gas solubility, reduce algae growth and curtail epizootic outbreaks.

Any amount of light, dim to bright, seems OK. Natural or synthetic water makes no difference in terms of vitality or reproduction in captivity. A pH of 7.5 to 8.3 is favored; no ammonia, nitrite and as low a concentration of nitrates as practical is the rule as with most marines.

Acclimation:

Many people take the risk of introducing pests, parasites & pollution by using a "floating & mixing" technique, pouring the damsels into their system. Don't do it! At the very least, appropriate procedure should involve bringing temperatures about equal, a freshwater dip with or without formaldehyde &/or copper & if possible, a two week quarantine.

Damselfishes are a group that are better to start feeding as soon as possible. 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.

Display:

1) Territoriality may be alleviated by under-crowding, one or less per 5-10 gallons, and providng plenty of cover.

2) If possible, buy a batch and introduce them to a new damsel-free tank all at once. If not possible/practical to do, move the tank decorations around, upsetting territories, when introducing new specimens.

3) They like hiding spaces. Provide coral, shells, plants- some nooks and crannies for social-psychological shelter. Keep the number and type of decorations simple to facilitate removal for cleaning, and possibly netting out livestock.

4) Some damsels, especially when they get larger and more aggressive, should be displayed with no other damsels. Examples include neon-velvets, dominos, hawaiian dascyllus, giant sea of cortez, garibaldis. Keep your eye on your populations and move those bullies. Maintaining these with larger angels, tangs, most triggerfishes, etc. tones them down a peg.

5) Be aware that small damsels are a dietary mainstay for most fishes whose mouths are large enough to accommodate them. Measure those lionfishes and basses before introduction.

Feeding:

Some damsels are specialized planktivores to herbivores in the wild. In captivity damsels accept all foods greedily. In fact, sargent-majors are legend for their use in training other shy species to surface feed.

Frequent small feedings 2-3 times per day of a mix of foods sustains them well. Nutritional diseases are all but unknown in this family.

Infectious and Parasitic Disease:

Damselfishes are parasitized internally and externally by several species of sporozoans, Crytocaryon, Oodinium, roundworms, flukes tapeworms and crustaceans. The presence, abundance and susceptability of these pathogens to varying salinities and treatments is complex. Damsels for the most part are disease resistant and if preventative measures have been executed and their environment is optimized you can expect low parasite loads.

Most treatable conditions (external) can be excluded by the freshwater dip treatment and low specific gravity mentioned before. Damselfishes respond well to periodic prophylactic copper treatments. Internal "worm" parasites are sometimes easy to diagnose but difficult to cure. For internal problems, most preventative and treatment therapeutics can only be applied via food; injection or bath for internal parasite control should be avoided for these fishes as they will probably do more harm than good.

Territoriality

This can be a type of social disease. Keep your stock under-crowded, and observe them daily for extreme interactions. Remove all bullies. Inter-specific aggression is probably the single largest source of damselfish mortality.

How long do they live? Some damsels have been kept in captivity for more than ten years and known to have lived more than twenty in the ocean.

Reproduction:

Most damsels reproduce like many substrate spawners; their behavior is similar to typical central-American neo-tropical cichlids. Other similarities with their contrasting freshwater cousins include an incomplete lateral line, a toothless palate, single, continuous dorsal fins and territorial behavior.

Other Biology:

Major areas of interesting damselfish biology will not be explored here. Chemical and sound communication, breeding and other behavior are rich adventures to be explored in a literature search and in you own tanks.

With the permission of Robert (Bob) Fenner webmaster of WetWebMedia (robertfenner@hotmail.com)

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