Saltwater Fish · Damselfish
Azure Damselfish
Chrysiptera hemicyanea
Electric-blue jewel with a yellow-washed bellyBeginner
- Lifespan
- 5-10 years
- Size
- About 6-7 cm (2.4-2.75 in)
- Social needs
- Territorial; best as the only damsel
- Time
- Daily feeding; weekly testing/changes
- Cost
- Medium
- Diet
- Omnivore (marine flake/pellet, mysis, algae)
Overview
What is this animal?
- 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.
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.
A good fit for
- Beginners wanting a hardy first marine fish
- Reef tanks - fully coral-safe
- Smaller marine setups from 110L/30 gal
- Keepers on a tighter livestock budget
- Adding intense colour without a big fish
Common mistakes to avoid
- Being sold as a cycling fish - never do this
- Mild for a damsel still means territorial
- Adding it before calmer tankmates
- Nearly impossible to catch out of live rock
- Bullying timid fish in small tanks
Enclosure
Minimum 110 litres (29 US gallons)
Must be housed alone. Territorial; best as the only damsel
- 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.
Supplies
Setup
- Tank, stand and sump
- Return pump and powerheads
- Protein skimmer
- Reef lighting
- Rock and sand
- Salt mix, refractometer and test kits
- Quarantine tank
Ongoing
- Marine flake or small pellet
- Frozen mysis shrimp
- Frozen brine shrimp
- Frozen cyclops or copepods
- Algae-based marine food
- Small thawing cup and strainer
- Turkey baster for spreading food in the current
Safe substrate: Aragonite sand · Dry or cured live rock · Bare bottom
Care routine
Daily
- Check salinity, temperature and flow
- Feed
- Head-count and look everyone over
- Top up evaporation with fresh water
Weekly
- Service the skimmer and filter socksevery 3 days
- Clean the glass
- Count the group
- Test the water
Monthly
- Water changeevery 2 weeks
- Calibrate the refractometer
- Check salt, RO/DI and reagents
Less often
- Deep-clean pumps and powerheadsevery 3 months
- Replace RO/DI filter mediaevery 6 months
Vet: Quarterly group and aggression review — every 3 months
Top resources for more info
Independent creators and organisations we would send a friend to. We have no affiliation with any of them, and nothing here is sponsored. Links checked 2026-09-19.
YouTubers
HumbleFish & ReefSaltwater fish disease, quarantine and treatment (Humble.Fish forum)BRStvReef tank setup, fish health and quarantine series (run by a retailer)FishOfHex AquaticsBeginner saltwater guides, avoiding common mistakes and tank disasters
Sites
Go deeper
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.
Is your enclosure big enough?
Minimum volume110 litres (29 US gallons)
CompanyMust be housed alone. Territorial; best as the only damsel
Is this urgent?
In a reef, stability matters more than any single target number. A parameter moving fast does more damage than a parameter sitting slightly off.
Go now
Any detectable ammonia or nitriteWater change now with matched, mixed and aerated saltwater. Stop feeding. Directly toxic, and a marine system has less margin than a freshwater one.
NowTemperature or salinity has moved sharplyCorrect slowly, over hours, not minutes. Check the heater and the top-off. The speed of the change does the damage. Correcting fast repeats the injury in the other direction.
NowRapid gilling, or a fish hanging in the flow breathing hardIncrease aeration and check temperature and salinity. Warm water holds less oxygen, and a heater failure shows up here first.
NowToday
White spots, or a fine dusting like icing sugarIdentify which parasite before treating. Most reef tanks cannot be treated in place. The two common parasites look similar and need different handling; velvet can kill a tank in days.
TodayCorals closed for more than a day, or receding tissueTest alkalinity first, and compare it against the last reading rather than a target. Unstable alkalinity is the most commonly cited coral killer, and a swing shows up in the trend, never in a single point.
TodayA new fish added without quarantine now looks unwellRemove it to a separate system today if you can. Nearly every wipeout in a reef tank traces back to a skipped quarantine.
TodayQuarantine every new animal, including corals and inverts. It is the single practice that separates a reef that lasts from a reef that restarts.
This is general guidance for a healthy adult, not a diagnosis. An exotics vet who knows your animal always overrides it — and the time to find one is before you need one.
What it really costs
Setup, monthly, first year and across a whole life, itemised and with the electricity worked out from the actual wattage. Published figures for the same animal disagree by a factor of four, so the calculator shows ranges rather than picking one.
Bedding and substrate
In a marine system the rock and the sand are life support, and how you start them decides the first six months.
Safe
Aragonite sandThe standard marine substrate. Buffers pH and hosts the biology.
safeDry or cured live rockDry rock avoids importing pests but takes longer to mature. Cured rock is faster and riskier.
safeBare bottomCommon in high-flow systems. Easier to keep clean, but it removes a large part of the biological buffer.
safeWith a caveat
Deep sand bedsPowerful nutrient processing when they work and a sulphide release when they are disturbed. Choose shallow or deep deliberately, not by accident.
with a caveatUncured live rockIt will cycle the tank for you, and it will also bring in whatever was living in it.
with a caveatNever
Silica play sandDoes not buffer, and it is commonly blamed for feeding diatom blooms in a new tank.
neverAny rock or decor of unknown originMetals and phosphate leach for months and are almost impossible to trace once the tank is running.
neverThis is our general list for saltwater fish. We have not built one specific to Damselfish yet.
My kit says 0.25 ppm. Is that dangerous?
A liquid kit measures total ammonia, but only the un-ionised fraction is really toxic, and that fraction is governed by pH and temperature — each whole pH unit multiplies it roughly tenfold. So the same reading can be nearly harmless in one tank and lethal in another; this works out which one you are in.
Compare with other animals
The same axes for every animal, side by side — the way the guides are written makes that a fair comparison rather than two articles.
Keep going
Damselfish, side by side
Same axes, same care guides — the honest way to choose between types.
See all Damselfish side by side →
