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Fish · Damselfish

Domino Damselfish

Dascyllus trimaculatus (Rüppell, 1829)

Also called Domino Damsel, Threespot Dascyllus, Three Spot Domino Damselfish, Domino, Domino Yellowbelly, Golden Domino Damsel (yellow-finned Fiji and Tonga form), Tongan Golden Domino Damsel

Reviewed by admin on October 29, 2026 · Meet the team

  • CareEasy
  • Reef safeYes
  • TemperamentAggressiveTerritorial; bullies smaller and newer fish
  • Favorite foods
    1. Frozen mysis / brine shrimp
    2. Marine flakes and pellets
    3. Herbivore / algae foods
  • Max size5.5 in (14 cm)
  • Min tank75 gal
  • LifespanNo published lifespan figure was found…
  • IUCN statusLeast Concern

Shop this species (1 in stock)

Domino Damselfish (Dascyllus trimaculatus)
Illustration, not a photo of this species.

Quick answers

How big does the Domino Damselfish get?
Up to 5.5 in (14 cm).
What size tank does it need?
At least 75 gallons.
How hard is it to keep?
Care level: Easy.
Is it reef safe?
Yes. Leaves corals and most invertebrates alone, though it may pick at small bottom-dwelling crustaceans.
What does it eat?
  • Frozen mysis / brine shrimp
  • Marine flakes and pellets
  • Herbivore / algae foods
How long does it live?
No published lifespan figure was found in the sources checked.
What are good tankmates?
  • Larger tangs
  • Large angelfish
  • Robust wrasses
  • Community-safe triggerfish
  • Other sturdy fish of similar or larger size added first

The 30-second version

The domino damsel is a black fish with white spots. A young one has three spots. There is one on each side and one on its head. That is why it looks like a domino! As it grows, the black turns gray and the spots get small. Some, from near Fiji and Tonga, have yellow fins. Babies hide in a big sea anemone, just like clownfish do. Some even share an anemone with clownfish. Others hide between the long spines of a sea urchin. Grown-ups live in groups near big rocks and coral. They eat tiny floating animals and bits of algae. The dad makes a nest and guards the eggs. In a tank it grows big and gets bossy, so it needs a large tank and tough tankmates.

Water & care

Extremely hardy and an eager eater, so retailers rate it Easy. The catch is size and temperament: a cute 1-inch juvenile grows into a 5-inch, very territorial fish that dominates small tanks. Plan for a large tank (Quality Marine suggests 75 gallons), plenty of rockwork, and robust tankmates, and add it last. Juveniles can be kept in a small group, but aggression rises as they mature. Add it only to an established, cycled tank.

ParameterKeep it at
Temperature 72–78 °F
Salinity (SG) 1.020–1.025
pH 8.1–8.4
Alkalinity 8–12 dKH

Ranges from Quality Marine and LiveAquaria. The fish has no specific calcium, magnesium, nitrate or phosphate target; follow your corals' needs in a reef. It tolerates poor water better than most fish, but that is not a reason to keep it in poor water.

Feeding

DietOmnivore

Favorite foods

  • Frozen mysis shrimp
  • Frozen brine shrimp
  • Marine flakes and pellets
  • Spirulina and other algae-based foods

Offer a mix of meaty and algae-based foods, including spirulina, in small meals once or twice a day or more. In the wild it eats algae, copepods and other plankton, so small foods that drift in the water column suit it.

Tank & maintenance

Minimum tank
75 gallons
Aquascape
Plenty of rockwork with caves and crevices for grazing and hiding, plus open swimming space. Rearranging the rockwork before adding new fish can break up an established territory.
Lighting
No special needs.
Water flow
Moderate; it is an active swimmer.

Routine upkeep

Routine upkeep: regular partial water changes and normal testing. Quarantine new fish for 2-4 weeks. Watch for bullying whenever a new fish is added, and be ready to rehome a domino that outgrows its tank or its tankmates.

Temperament & tankmates

TemperamentAggressive

LiveAquaria, Quality Marine and Saltwaterfish.com all rate it Aggressive. Adults defend a territory hard and chase newcomers, timid fish and other damsels. Keep one per tank in most home aquariums (or a juvenile group in a large tank), add it after other fish, and choose larger, sturdy tankmates that are not easily harassed.

Reef safeYes

Leaves corals and most invertebrates alone, though it may pick at small bottom-dwelling crustaceans. Juveniles may settle into an anemone, and a large adult can stress smaller fish more than it stresses the reef itself.

Good tankmates

  • Larger tangs
  • Large angelfish
  • Robust wrasses
  • Community-safe triggerfish
  • Other sturdy fish of similar or larger size added first

Avoid

  • Other damselfish in small tanks
  • Small, timid fish such as gobies, firefish and dartfish
  • Clownfish in small tanks (they compete for anemones)
  • Predators large enough to swallow it

Help it thrive

  • Buy it knowing it will grow to about 5 inches; pick a tank of 75 gallons or more.
  • Add it last, after peaceful fish have settled in.
  • Choose sturdy tankmates of similar or larger size.
  • Feed a varied diet that mixes meaty foods with spirulina or other algae foods.
  • Give it plenty of caves so it can claim a home without taking over the whole tank.

Common ailments

Marine ich (Cryptocaryon irritans)
Signs
White, salt-grain spots on the body, fins or gills, scratching against rocks, cloudy eyes, faster breathing and loss of appetite.
Prevention
Quarantine all new fish, avoid temperature swings and keep stress low.
Treatment
Treat every fish in a hospital tank with copper or chloroquine phosphate, or use the tank-transfer method; none of these belong in a reef display. The cyst stage can last up to 72 days, so leave the display without fish for about 11 weeks.

Marine velvet (Amyloodinium ocellatum)
Signs
A fine, dusty sheen on the skin, very fast breathing, gasping at the surface, scratching and sudden deaths, sometimes within 12-48 hours.
Prevention
Strict quarantine, and separate nets and buckets for quarantine and display tanks.
Treatment
Act immediately: a temperature- and pH-matched freshwater dip for quick relief, then copper or chloroquine in a hospital tank, and a fishless fallow period for the display.

Fighting injuries
Signs
Torn fins, missing scales and a fish that hides constantly; usually the domino's tankmates, but sometimes the domino itself when kept with other damsels.
Prevention
Give it a large tank, add it last, and avoid other damsels and small, timid fish.
Treatment
Separate the injured fish, keep the water very clean so wounds heal without infection, and rehome the aggressor if the bullying continues.

This is general hobby guidance, not veterinary advice. Quarantine new arrivals and treat in a separate tank whenever you can.

Risks of owning one

  • Grows to about 5 inches and becomes one of the boss fish in most home tanks.
  • Bullies new, small or timid fish, which can make it hard to add fish later.
  • Its low price and cute juvenile look tempt people to buy it for tanks too small for the adult.
  • Wild-caught, so new fish can bring in ich or velvet; quarantine is essential.
  • Juveniles may compete with clownfish for an anemone.

Breeding

DifficultyHard Captive-bredRare or wild-caught

Nest-spawning egg-layer. Males court females with a 'signal jump', spawn in a nest and guard and aerate the sticky eggs. FishBase reports a captive pair that spawned about three times a month, 17 times over seven months. Raising the tiny planktonic larvae is a research-level project, and no commercial captive-bred supply was found.

  1. Keep a well-fed pair in a large tank without egg-eating tankmates.
  2. Watch for the male's 'signal jumps' and for a cleaned nest site on rock.
  3. Leave the male to guard the eggs until they hatch.
  4. Collect the larvae into a separate rearing tank with green water and rotifers.
  5. Expect heavy losses; rearing damselfish larvae is still experimental for hobbyists.

Deep dive The science, history and family tree

The science

Dascyllus trimaculatus is a robust, deep-bodied damselfish (Pomacentridae) that reaches about 14 cm total length. Juveniles are black with bluish scale centers, a white spot on each side and a white blotch on the forehead; with age the black fades to dusky grey and the spots shrink or disappear. It is one of the most widespread damselfishes, ranging from the Red Sea and East Africa to the Line and Pitcairn islands, north to southern Japan and south to Sydney, but it is absent from Hawaii and the Marquesas, where close relatives live instead. Adults form small to large groups around coral heads and rocks from the surface to 55 m. Juveniles shelter in large sea anemones, among the spines of sea urchins or in small coral heads, sometimes sharing an anemone with clownfish. The diet is algae, copepods and other planktonic crustaceans. Males court with a 'signal jump', and they guard and aerate the sticky eggs. Unlike most Dascyllus, which change sex, this species has separate sexes. Around Fiji a yellow-finned form appears to carry genes from the golden domino, D. auripinnis. The IUCN lists it as Least Concern.

Appearance
Juveniles: jet black with bluish scale centers, one white spot on each side of the body and a white blotch on the forehead. Adults: dusky grey to black, the spots smaller or missing, the forehead spot sometimes absent. South Pacific form: fish from Fiji (and those exported from Tonga as 'Domino yellowbelly' or sold as 'golden domino') have yellow pelvic and anal fins and orange streaks in the dorsal fin and tail, and look intermediate between this species and the Golden Domino Dascyllus (D. auripinnis), which has almost solidly yellow belly fins and lives only in the Line, Phoenix and northern Cook islands. LiveAquaria lists its golden dominos as 'Dascyllus cf auripinnis' and describes the gold as appearing with age. Other look-alikes: the Hawaiian Dascyllus (D. albisella) and Strasburg's Dascyllus (D. strasburgi) of the Marquesas.
Native range
Indo-Pacific: Red Sea and East Africa to the Line and Pitcairn islands, north to southern Japan and south to Sydney, Australia; absent from the Hawaiian and Marquesan islands (FishBase). Recorded from Tonga (FishBase country checklist), where it is exported for the aquarium trade.
Habitat
Coral and rocky reefs from the surface to about 55 m. Adults gather in small to large groups around coral heads or large rocks. Juveniles shelter in large sea anemones such as Stichodactyla, among the spines of Diadema sea urchins, or in small branching coral heads, and may share an anemone with clownfish; they lose the anemone habit as they mature.
Size
5.5 in (14 cm). FishBase gives 14 cm TL and Wikipedia 13 cm; Quality Marine says almost 6 in. LiveAquaria gives 4.5 in for its golden domino listings. Most are sold small, but they grow quickly.
Lifespan
No published lifespan figure was found in the sources checked. FishBase rates the species as highly resilient, with a minimum population doubling time under 15 months.
Conservation
Least Concern. IUCN Least Concern (assessed 2021); listed as Vulnerable in the Persian Gulf. Not listed by CITES. Commonly collected for the aquarium trade, mostly wild-caught; no commercial captive-bred supply was found

In the aquarium vs in the wild

In your aquarium

A very hardy, bold display fish for larger fish-only or reef tanks with robust tankmates.

On the reef

An abundant plankton picker on Indo-Pacific reefs; juveniles use anemones, urchins and small corals as nurseries, sometimes sharing them with clownfish.

History

Eduard Rüppell described the species from the Red Sea in 1829 as Pomacentrus trimaculatus; 'trimaculatus' means 'three-spotted', after its three white spots. It is commonly seen in the aquarium trade because it is hardy and striking as a juvenile. In 2001 Randall and Randall described the Golden Domino Dascyllus (D. auripinnis) from the central Pacific, and yellow-finned dominos from Fiji and Tonga have since been sold under that name, although D. auripinnis is not recorded from Tonga and DNA work suggests the yellow Fijian fish are D. trimaculatus with some auripinnis genes.

Evolution & relatives

Dascyllus is a genus of about a dozen damselfishes split into three species complexes. The domino belongs to the trimaculatus complex with the Hawaiian Dascyllus (D. albisella), Strasburg's Dascyllus (D. strasburgi) and the Golden Domino (D. auripinnis); this complex split from the reticulatus complex about 3.9 million years ago, and all its members live with anemones when young. Mitochondrial DNA splits D. trimaculatus into Indian Ocean, southern French Polynesia and West-Central Pacific populations, and D. auripinnis falls inside the West-Central Pacific group, which raises doubts about its separate status. Unlike the other complexes, which change sex from female to male, the trimaculatus complex appears to have lost sex change.

Family tree, from kingdom down

  1. Kingdom Animalia Animals Animals are living things made of many cells that must eat food to live. Fish, corals, crabs, snails and sea stars are all animals.
  2. Phylum Chordata Chordates Chordates have a stiff rod running down their back at some point in their lives. In fish and people, this rod is replaced by a backbone.
  3. Subphylum Vertebrata Vertebrates Vertebrates are animals with a backbone and a skull. Fish, frogs, birds and people are all vertebrates.
  4. Infraphylum Gnathostomata jawed vertebrates
  5. Parvphylum Osteichthyes bony fishes
  6. Gigaclass Actinopterygii ray-finned fishes
  7. Superclass Actinopteri
  8. Class Teleostei Teleost fishes Teleosts are bony fishes with thin, bendy fin rays and jaws that can push forward. Almost all of the fish in the world are teleosts.
  9. Order Ovalentaria (unplaced) Unplaced ovalentarian fishes Ovalentaria is a big group of fish with spiny fins. Scientists found it by studying DNA, and most of its fish lay eggs that stay stuck to the bottom. 'Incertae sedis' means 'place not sure': scientists have not settled which order damselfishes, dottybacks and basslets belong in.
  10. Family Pomacentridae Damselfishes and clownfishes Damselfishes are small, often colorful reef fish that guard their homes. Clownfish and chromis are damselfishes.
  11. Genus Dascyllus humbugs and dominos
  12. Species Dascyllus trimaculatus

See it on the Tree of Life Compare with another species

Closest relatives

  • Dascyllus auripinnis Golden Domino Dascyllus Same complex; Line, Phoenix and Cook islands look-alike with yellow fins
  • Dascyllus albisella Hawaiian Dascyllus Same complex; replaces it in Hawaii
  • Dascyllus aruanus Three Stripe Damselfish Same genus; aruanus complex
  • Dascyllus reticulatus Two Stripe Damselfish Same genus; reticulatus complex Read guide · Compare

Fun facts

  1. Its three white spots, two on the sides and one on the forehead, are why it is called a domino.
  2. Young dominos often hide in sea anemones, and sometimes share them with clownfish.
  3. Dominos recognize their own kind by sound.
  4. Some dominos from Fiji have yellow fins because their ancestors mixed with the golden domino.
  5. A captive pair once spawned 17 times in seven months.

Learn more

Sources

  1. WoRMS: Dascyllus trimaculatus (Rüppell, 1829) marinespecies.org
  2. FishBase: Dascyllus trimaculatus (Threespot dascyllus) fishbase.se
  3. Wikipedia: Threespot dascyllus en.wikipedia.org
  4. Wikipedia: Dascyllus en.wikipedia.org
  5. Quality Marine: 3 Spot Domino Damselfish qualitymarine.com
  6. LiveAquaria: Golden Domino Damselfish liveaquaria.com
  7. FishBase: Tonga country checklist (Pomacentridae) fishbase.se
  8. LiveStockUSA: Tonga Fish & Inverts price list livestockusa.org

Scientific names and classification follow the World Register of Marine Species (AphiaID 212846). Checked by our team. Last updated October 29, 2026.