Domino damselfish (Dascyllus trimaculatus) are also known as three-spot damselfish because they are black fish with three small white spots on their bodies. The name domino damsel was also derived from their appearance - they are said to resemble dominos. The three white spots are located on top of the fish's head and on each side of the upper body.
They are able to tolerate water conditions that a lot of other saltwater fish cannot and are therefore a good choice when you are new to keeping saltwater fish.
Domino damsels belong to the family Pomacentridae, which includes the other damselfish and the anemonefish.
Like many other members of the family Pomacentridae, domino damsels have a symbiotic relationship with sea anemones, especially when juveniles.
In their natural habitat they inhabit coral reefs in the Indo-Pacific and are often found in groups as shown in the above photo.
In the aquarium they can sometimes be kept in groups, but are somewhat territorial toward members of their own species.
For a demonstration of this territorial behavior, as well as the damselfish's symbiotic relationship with sea anemones, watch the short You Tube video below:
As you can see from the video, the damselfish was perfectly okay sitting in the sea anemone with other fish species swimming nearby. However, as soon as another domino damsel came near, the domino damsel that was resting in the anemone chased it away.
You should provide plenty of live rock and hiding places in their tank.
Domino damselfish are omnivores - eating both plant-based and meaty foods. They eat algae as well as other aquarium fare for marine fish.
They make excellent additions to a reef tank as they rarely bother the inhabitants. However, they do sometimes bully smaller, less aggressive fish species as well as other domino damselfish. They tend to become more aggressive as they age. They are small fish (only about 5 inches (13 cm)), but they can be pugnacious.
Even though these fish are pretty and have interesting personalities they are relatively inexpensive for saltwater fish - domino damselfish can usually be purchased for about $4-5 each.
They will spawn in the aquarium.