|Distribution||Eastern Indian Ocean|
|Maximum Size||6cm (2.4")|
|Sexual Dimorphism||No obvious external differences. Males in breeding dress may appear an overall brighter colouration compared to the females. However, this is not a given.|
|Temperature||Tropical: 23-27 deg C (73-81 deg F)|
|Water Parameters||SG: 1.020-1.025, pH: 8.1-8.4|
|Lighting||No special requirements|
|Reef Aquarium Compatibility||Excellent|
The Blue Star Damselfish is known from inshore areas and outer reef slopes, usually staying close to the corals living amongst the mixed rubble substrate. Adults tend to congregate in small groups over favourable sections of reef, feeding on the zooplankton in the water column and to a lesser extent, benthic algae. Blue Star Damselfish are colourful, hardy, and well suited to the reef aquarium. However, this is a fairly aggressive species, and as these fish mature, their belligerence also often increases. It is therefore advisable to keep either a single specimen, a known male-female pair, or a large sized odd-numbered shoal (9+) introduced simultaneously as juveniles into a spacious tank with plenty of hiding places amongst the rockwork. Small groups are often known to suffer fatalities. Choose tankmates with care, avoiding any really docile species such as firefish and cardinalfish. This vibrant species was named after Dr Gerald Allen, one of the world's leading authorities on damselfishes.
Offer a varied diet, including meaty items such as Mysis shrimp, vitamin-enriched brineshrimp, chopped krill, also marine flake food, and herbivore rations. Feed small amounts 3 times per day.
These fish form distinct pairs when breeding. The tiny eggs (numbering up to 1000) are deposited in a cave or on the substrate and are guarded and aerated by the male fish until hatching.