Domino damselfish or Dascyllus trimaculatus are classified to family Pomacentridae. This species is a native of the Indo-Pacific with an established presence stemming form the shorelines of southern Japan to Australia.

These fish received their names from their distinctive color pallets. They have black bodies just like a domino. There are three large white spots their bodies, one on each side and one on their forehead. They are also called threespot dascyllus and domino damsels. They commonly grow to as long as 5 inches in length and have a life expectancy of up to 10 years in captivity. These fish can swim in depths up to 200 feet.

This is one tough and highly adaptable little fish. They can tolerate conditions that would kill a less hardy species. This capability of surviving adverse environmental conditions has lead to them being a popular biological stabilizer for aquarists who are cycling a new tank. If the damselfish lives it is ok to risk introducing more expensive and temperamental species to the new aquarium.

This is not a timid creature by any means. They have a propensity to be downright tenacious for a fish of their stature. The level of aggressiveness increases as they mature. Housing them with smaller and more docile species may prove problematic. They will also exhibit territorial behavior toward members of their own species especially in smaller aquariums. Suitable tank-mates include dwarf angelfish, puffers, and cardinalfish.

A common trait among damselfish is their symbiotic relationship with sea anomies. They are commonly referred to as anomiefish because of this inherent mutualism. Sea anomies exude neurotoxins which can be deadly to most other fish. Damselfish have a natural immunity to these toxins which inevitably leads to mutually beneficial coop between the two species. Dominoes feed on the semi-digested matter left floating around the anomie because of its dietary habits and remove harmful parasites from the creature. There is the additional benefit of being able to seek shelter within the tentacles of a species even the most aggressive of predators will instinctively steer clear of. In return for shelter and provisions Dominoes excrete fecal matter which is a source of nutrition for the anomie. Dominoes also associate with diadema sea urchins and branching coral.

This is an omnivorous species. Part of their diet in the wild consists of ingesting various species of algae. It is recommended that you provide them with an abundance of live rock to graze on. The live rock will provide them with both the plant matter necessary for their nutritional requirements and make for acceptable hiding place in the absence of their symbiotic partners.

In addition to plant matter they can be fed brine shrimp, chopped fresh shrimp. mollusks, or squid. They will also eat marine flakes for omnivores.

Like their cousins the clown fish, dominoes are sequential hermaphrodites. They are all born as males. If you place two males in an aquarium together the larger more dominant fish will undergo a gender change. This species has been known to breed in captivity.

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