Dascyllus trimaculatus

Common Names: Threespot damsel, domino damsel, nasty little fish

Type Locality: Massawa, Eritrea, Red Sea

Range: Red Sea and East Africa to the islands of Oceania excluding the Hawai'ian and Marquesas Islands; north to Japan and south to Australia.

Taxonomic Troubles: Originally described as Pomacentrus trimaculatus

Size: 11 cm (4.3 inches) SL

Preferred Water Chemistry: Tropical marine

Difficulty: Extremely hardy and easy to feed

Tank Setup: A reef tank is ideal. This fish may associate with a coral or an anemone, much like a clownfish. Due to its territoriality, this damsel is best added after other fish have had a chance to settle in. Of course, its hardiness often makes it a choice for

Feeding: Will usually take any aquarium fare but should have quality live, frozen, or freeze-dried foods, as well as ample algae for grazing.

Breeding: Often breeds int he aquarium; its availability and low price provide little incentive to commercially raise the young.

Fish Description

The bold markings of white spots on a jet black background coupled with an outgoing personality make this fish very popular, but as the fish grows, the black dulls to grey, the white spots often fade, and the fish becomes downright nasty.


Many people consider this the hardiest marine fish. It is certainly undemanding and extremely tolerant of beginning marine aquarists' fumbling. Unfortunately, it can be very intolerant of any other fish in its tank. Bought as a cute little domino, this fish quickly endears itself to its owner with its striking coloration, jaunty style, and perky attitude. It often swims vertically like a little elevator.

Like many marine fishes, however, it becomes less cute and adorable as it grows, turning nondescript and highly aggressive. In fact, this little fish is feisty to the extreme. Males defending their nest have been known to attack (and bite) divers! Territorial and nippy, it can make life miserable for other fish, though it leaves sessile invertebrates alone--except for occasionally living harmlessly among them--so it's reef safe.

Almost all damsals are aggressive, and the domino damsel is one of the most aggressive of damsels. THeir aggression is often strongest against their own kind, which is very disappointing, since a group of these fish would be an impressive display otherwise. In a sufficiently large tank with enough hiding places, you may be able to maintain more than one. Obviously, since people have them breeding in their tanks, they have at least two together.

This fish is most often successfully kept in a tank of mixed damsels, or with tankmates that are considerably larger. Juveniles are much less aggressive, and raising them together with other fish gives the best chance of getting a workable mix--but there's no guarantee. Another possibility is to maintain one of these damsels by itself as a pet, much the way many cichlids are kept.

Certainly as close to bullet-proof as any marine fish can be, the domino damsel often launches an aquarist into the marine hobby successfully but then winds up being a problem later on. This can be avoided by understanding the animal's needs before purchasing it.