The Beautiful Ducklings that turn into Ugly Swans:
Damsels of the Genus Neoglyphidodon

By Steven Pro

 

Most readers should be familiar with the story of the young ugly duckling that turned into a beautiful, fully-developed Swan.  Well, the fish in this genus are the exact opposite.  They are little, cute, and attractive as juveniles, but become big, ugly bruisers as adults, making many of their keepers regret the decision to purchase them in the first place.

Classification:

Damsels, along with their relatives, the Clownfishes, make up the family Pomacentridae. This family consists of 28 genera and 321 species (Fenner, 2001). The genus Neoglyphidodon has eight species (Michael, 2001), but only three are commonly offered for sale with a fourth occasionally available.

Neoglyphidodon Species

Selection:

It is usually quite easy to find a healthy specimen in this genus. I generally avoid any newly-arrived fishes, preferring to wait until they have been in the dealer's tank for at least a few days to a week. This practice is especially important when dealing with damsels. They are cheap, and unfortunately are treated as such. Typically, they are shipped in small bags with very little water to save on freight charges. For those of you that don’t know, freight makes up a significant portion of the final purchase price of marine ornamentals.  That means they are prone to suffer from Post Traumatic Shipping Disorder or Delayed Mortality Syndrome, depending on whose works you read.  Morgan Lidster of Inland Aquatics coined the first phrase, while Edward Noga described the latter.  Both phrases are terms to encompass the broad number of reasons that an animal could die shortly after shipping such as temperature extremes, low dissolved oxygen, depressed pH and so on.  These terms specifically exclude more widely recognized diseases such as parasites or bacterial infections.  Generally, once they have remained in a dealer's tank for three days to a week or more, I would consider them safe enough to purchase. Even after being held that long at the dealer, I would still suggest that these fish undergo a proper quarantine period just like any other addition to the display.  Quarantine allows new fish to be screened for disease, adjust to prepared foods and gain some weight before being thrust into the competitive environment of the display.

Also, I would discourage my fellow aquarists from purchasing extremely small damsels, sometimes as small as a dime or even smaller.  Personally, I avoid these specimens like the plague. In my experience, many of these tiny specimens suffer greater mortality than their slightly larger counterparts. As a general rule for any fish purchases, the smallest and the largest individuals should be avoided (Fenner, 2001). In my experience, the babies that come through the chain of custody have a high mortality rate. It is my opinion that these are half starved by the time they get to the local dealer's tanks where they may receive routine feedings. Also, they don't tolerate shipping nearly as well as slightly larger specimens.  On the other end of the spectrum, the largest adults often refuse to eat prepared foods. I believe they have simply been in the wild for too long to adjust to life in captivity, although that is usually not as big of a problem with damsels as with other genera.

Finally, I avoid specimens from a tank containing other dead or dying fish. Whether the deaths can be attributed to shipping problems, aggression, disease, etc. makes little difference. All are signs that aquarists should avoid specimens from that shipment or that dealer for the time being.

Care:

Damsels, in general, are hardy fish that are not especially demanding of water quality. Many times, these fishes are purchased by inexperienced aquarists and used to cycle new aquariums (a practice which I discourage), and consequently they are exposed to high levels of ammonia and nitrite and generally subjected to less than ideal conditions as the new hobbyist “learns the ropes”. Despite the abuse they endure, they often thrive nonetheless. But as standard practice for a conscientious aquarist, we should all remember that we are talking about live animals and should strive to provide them with the best environment possible.

They should be given plenty of cover so that they may setup territories to defend. While most stores keep their tanks intentionally crowded in an effort to minimize aggression, this is only a short-term solution. For long-term regular care, they should be given ample room and overcrowding should be avoided for both the stress that it imposes as well as its impact on water quality. Furthermore, be prepared to thin out the group. Usually a dominant individual or pair develops if a small group is purchased and introduced at the same time. This lone alpha or top pair then typically goes on a rampage, aggressively harassing all others of the same species. That is simply the price to pay for keeping these fishes, so plans should be made accordingly.

In general, damsels readily accept a variety of foods, and Neoglyphidodon species are no different.  They seem to forage a lot based on their reported food items (www.fishbase.org).  They feed primarily on algae and plankton, but are also mentioned to consume some soft corals, sponges, and tunicates.  This definitely brings into question how reef-safe this genera might be.

Compatibility:

As I already mentioned, most damsels are very territorial and the Neoglyphidodon are no exception. Care should be taken in selecting appropriate tankmates for these fish. They should be housed with other fish that are equally as scrappy, but remember that to many marine predators, damsels are the aquatic version of "popcorn" (Fenner, 2001). Many are bite-sized tasty morsels that can easily be gulped down by groupers, lionfish, eels and other predators, so plan accordingly.

Reproduction:

For those interested in breeding marine fishes, one of the fish in this genus (Neoglyphidodon melas) has been successfully bred and reared in captivity (Tanaka, Yoshinaka, & Hasegawa, 1996).  That is the good news.  The bad news is the paper that details the process is almost entirely written in Japanese.  Only the abstract and one chart are translated into English.  But there is still some useful information to be found here for those interested in the challenge of raising these fishes.  First and foremost, the larvae were successfully fed rotifers, Artemia nauplii (baby brine shrimp), fish eggs, and chopped meats.  And, the authors were able to raise 400 larvae to one year old juveniles.  They also recorded some very interesting observations on their breeding patterns as well as the hatching of the eggs, which are detailed in the chart below.

*    Eggs found first thing in the morning.

**  Eggs hatch sometime after dark.

As you can see from the chart, the fish are quite prolific.  They spawn on average every 10.4 days. And their eggs hatch usually 6-7 days later at 26.3-26.5°C (~74.1-74.4°F).  There was also something else interesting that I noticed.  The fish generally spawned in the evening (12 of 16 times), but there were several spawning events in the morning.  But regardless of when the spawning took place, the eggs always hatch in the evening hours, likely a good survival strategy for the larvae.  As to how pertinent this information is, I am unsure.  Attempting to breed and rear these fishes is likely only to be an exercise in larval rearing techniques and unlikely to be profitable due to the widespread availability and inexpensive wholesale price of their wild-caught counterparts.

Conclusions:

I am really not a big fan of this genus.  These fishes are territorial and not attractive as adults, so I find little reason to work around their aggression.  If they stayed pretty, I would be more willing to make sacrifices to keep them.  Unfortunately, a never ending supply of beginner aquarists who don’t research their acquisitions prior to purchase will always be attracted to the attractive juveniles, ensuring that they are likely to be staples in the trade for the foreseeable future.

References:

Fenner, Robert. 2001. The Conscientious Marine Aquarist. Microcosm/T.F.H. Publications, Neptune City, New Jersey, pages 269-273.

Lidster, Morgan. pers. comm.

Michael, Scott. 2001. “Good Damsel, Bad Damsel: The Best of the Bunch, part 2.” Aquarium Fish Magazine, December 2001, pages 42-51.

Noga, Edward. 2000. Fish Disease: Diagnosis & Treatment. Iowa University Press, Ames, Iowa, pages 238-239.

Tanaka, Yoichi, Atsushi Yoshinaka, & Etsuko Hasegawa. 1996. “Reproductive Behavior and Rearing of the Damselfish, Neoglyphidodon melas (Cuvier), in the Aquarium.” Bulletin of the Institute of Oceanic Research and Development, Tokai University, volume 17, pages 13-25.

Online References:

www.fishbase.org