Care
The Domino Damselfish, also known as the Three Spot Damselfish, is a resilient aquarium fish. In the wild, adult fish form large aggregations amongst rocky coral reefs; the juveniles often commensal with large anemones, small coral heads, and sea urchins.
Cheap and extremely hardy, juvenile Dominoes are very attractive and reef-friendly, but grow into extremely aggressive fish that are likely to terrorise their tankmates. As with all damsels other than clownfish, dominant fish become male. Social groupings consist of a single territorial male, one or more females and unsexed juvenile fish. In the aquarium a stable group can be created, ideally by mixing individuals of different sizes that duplicate this natural order, or allowing sufficient space for weaker fish to escape serious harassment until a dominant individual develops. Any new humbugs added should be significantly smaller than established ones, duplicating the recruitment of juveniles from the plankton. Expect the male to defend a spawning site vigorously from all intruders apart from females ready to spawn.
Their aquarium should be spacious and include plenty of rockwork to break sightlines and create hiding spots; try to aquascape it in such a way as to create several visual barriers as this will help to minimise aggression levels. Although hardy, good filtration is a must and decent water movement will be appreciated. Peaceful tankmates are likely to be killed in all but the largest aquaria.
Dominoes are an active, interesting species to keep but do need to be kept in a stocking scheme that is well thought out beforehand. Removing them from a well-furnished tank will be extremely difficult at a later stage and adding any new fishes can be extremely challenging. It's true to say that many keepers regret adding these long-lived fish to their aquarium as their hobby develops and the frustrations of being unable to add new fish sink in. Sadly, as these fish mature, the colour and pattern becomes somewhat drab, with the white markings much less apparent (sometimes to a point where they can't even be seen) and the black body colour takes on much more of a steely grey appearance with dark scale margins. Mature adults are very deep bodied fish. There are many reports of these bold fish biting the hands of their owners as they carry out maintenance on their tanks. No real harm should ensue, but they might make you jump!
Feeding
Offer a quality dry staple food to ensure good nutrition. This can be supplemented with frozen foods such as Mysis shrimp, krill, vitamin-enriched brineshrimp etc, plus herbivore flakes and greenfoods. Feed small amounts 2 or 3 times per day.
Breeding
Damselfishes readily spawn in the home aquarium. The male will entice a female to spawn in a pre-prepared nest area, after which he will vigorously protect the eggs. These usually hatch in 3-5 days, depending on temperature and other conditions. The planktonic larvae require specialist rearing but develop rapidly. Due to the aggressive nature of this fish and their limited value, few attempts have been made to rear Dascyllus damselfish in captivity as the resulting fish are not commercially viable.
