The Azure Damselfish is a thumb-sized reef fish in electric blue, with rich yellow flooding the belly, anal fin, and tail.
That extensive yellow underside separates it from the similar Yellowtail Damselfish (Chrysiptera parasema), whose yellow is confined to the tail.
In the wild it hovers over branching Acropora thickets across the Coral Triangle and darts into the coral at any threat.
At roughly 6-7 cm (2.4-2.75 in) it stays small, and it is hardy, inexpensive, and among the mildest-mannered of the damselfishes.
Unlike the shoaling, open-water Green Chromis, the Azure claims a patch of rock and defends it, so it is usually kept singly.
It suits a beginner who understands that mild for a damsel still means opinionated.
Damsels are often sold as disposable starter fish for cycling new tanks.
Never cycle a tank with live fish; run a fishless ammonia cycle and add the Azure to a fully established system where it can live out its 5-10 years.
Housing
House a single Azure in a fully cycled marine tank of at least 110L (30 gallons); more swimming room noticeably softens its territorial edge, so 150L (40 gal) or larger is better still.
Maintain salinity 1.024-1.026, temperature 24-27°C (75-80°F), pH 8.1-8.4, alkalinity around 8-12 dKH, ammonia and nitrite at zero, and nitrate below 20 ppm.
Aquascape with plenty of live rock offering branching, coral-like structure, since this species bolts into tight crevices at the first sign of a threat.
Add the Azure last, or among the last fish, so it cannot claim the whole tank as territory before calmer tankmates settle.
Once established in live rock it is notoriously difficult to net out, and removing a problem damsel often means dismantling the aquascape.
A tight-fitting lid prevents startled jumps.
Diet
Azure Damselfish are unfussy omnivores that pick zooplankton and filamentous algae on the reef.
Offer a quality marine pellet or flake as the staple, fed once or twice daily in small portions.
Rotate in frozen mysis and enriched brine shrimp several times a week, plus a spirulina or algae-based food to cover the herbivorous side.
They feed boldly from day one and rarely refuse anything, which is part of why they are so hardy.
That eagerness makes overfeeding the real risk, so keep portions to what disappears within a minute or two to protect water quality.
Health
This is one of the most disease-resistant marine fish available, and most Azures that die young are lost to new-tank problems or aggression rather than illness.
Marine ich (Cryptocaryon) and velvet (Amyloodinium) are the main disease risks, almost always introduced with unquarantined new arrivals.
Quarantine every new fish for several weeks before it joins the display.
Watch for white spots, scratching against rock, rapid breathing, or clamped fins as early warning signs.
In stable water with nitrate held low, an Azure commonly reaches 5-10 years, far longer than its bargain price suggests.
Its hardiness is exactly why it gets abused as a cycling fish; it deserves the same water quality as any delicate species.
Temperament
The Azure sits at the mild end of the damselfish spectrum and is completely reef-safe, ignoring corals and invertebrates.
Young fish are peaceful, but adults hold a territory around a favourite rock and chase fish that trespass.
In modest tanks (under roughly 200L / 55 gal) it is safest kept as the only damselfish.
Pair it with tankmates that can hold their own, such as clownfish, Royal Grammas, or similar-sized wrasses.
Very timid species like Firefish Gobies can be pinned into hiding by a mature Azure in a small tank.
A group of three or more is only realistic from 200L (55 gal) upward, added simultaneously with rockwork that breaks sightlines.
Beginner
Beginner
Beginner
Beginner
Beginner
Beginner