Blue Reef Chromis

Blue Reef Chromis (Azurina cyanea) is a streamlined brilliant-blue reef fish with dark margins on the dorsal and deeply forked tail fins. It feeds in the water column above outer reefs, capturing small zooplankton before retreating into reef shelter. Its combination of color, movement, and shelter use makes it an engaging aquarium fish when the environment is planned around the mature animal.

Native to Western Atlantic, Bermuda, southern Florida, Bahamas, and Caribbean reefs, this species needs a layout that reflects how it actually feeds and uses space. Keep a long open swimming lane beside several retreats; groups need a substantially larger display. Adult housing should be available from the outset or arranged before the fish outgrows its current system; a small purchase size does not reduce the long-term requirement.

Azurina cyanea is the accepted combination for the species formerly listed as Chromis cyanea. Adults need much more swimming room than their slender juvenile bodies suggest. Plan for an adult up to 5.9 inches total length and a recommended minimum aquarium of 75 gallons. Its care level is moderate, reflecting the habitat, feeding, and social considerations described below rather than hardiness alone.

Quick Care Guide

Care Level: Moderate
Minimum Tank Size: 75 gallons
Adult Size: Up to 5.9 inches total length
Temperament: Peaceful
Diet: Planktivore
Reef Safe: Yes
Region: Western Atlantic, Bermuda, southern Florida, Bahamas, and Caribbean reefs
Scientific Name: Azurina cyanea

Tank Requirements

Blue Reef Chromis requires at least 75 gallons for the adult housing described here, with a larger aquarium preferred when other fishes share its territory. Keep a long open swimming lane beside several retreats; groups need a substantially larger display. The footprint, shelter distribution, and room to disengage from other fish matter alongside the total volume.

Keep a generous stretch of open water above and beside the reef structure. These fishes feed while hovering or swimming away from cover, and a tank packed wall-to-wall with rock can lack usable feeding room despite its nominal capacity. A long footprint and clear turning space become increasingly important with growth.

Provide numerous individual retreats distributed through stable rock or branching-style structures. Fish need protected resting sites as well as open feeding water. Visual partitions help subordinate individuals move out of a dominant fish's sight, while multiple exits reduce the risk of one fish being cornered inside a desirable refuge.

Use broad, variable water movement that keeps fine food available without forcing constant swimming against a narrow pump jet. Maintain strong oxygenation, screened equipment, and a secure lid. Leave access to remove settled food because several small daily meals can otherwise accumulate organic waste beneath the rock.

Establish biological filtration and a consistent maintenance routine before introduction. Keep ammonia and nitrite undetectable and maintain good oxygenation. Hardy damsels must not be used to cycle an unprepared aquarium; tolerance of some conditions does not justify avoidable exposure to poor water quality.

The single-adult minimum must not be interpreted as a ready-made allowance for a school. Plan any group around the adult biomass, the number of usable refuges, and the ability of every fish to feed. Several small juvenile fish can become a very different stocking load after growth.

Diet and Feeding

Planktivore is the primary dietary classification for this species. Offer small mysis, copepods, cyclops, enriched brine shrimp, and complete small marine pellets.

The primary feeding strategy is capture of small suspended animal prey. Supply food through the water column rather than relying entirely on large sinking chunks or grazing surfaces. A fish that appears busy swimming with its companions can still receive too little nutrition if most particles are too large or faster fish clear the feeding lane.

Use a varied marine-based ration rather than one convenient food indefinitely. Complete preparations can supply a useful nutritional base, while suitably sized frozen foods provide variety and encourage normal feeding. Enriched brine shrimp is a supplement, not a guarantee of a complete diet by itself. Avoid freshwater feeder fish and oversized pieces that cannot be swallowed cleanly.

Feed modest portions at least twice daily, with three smaller offerings particularly useful for active plankton feeders and lean new arrivals. Keep food particles matched to mouth size, and watch actual swallowing rather than assuming that approaching a feeding station means the fish has eaten. Adjust the ration as the fish grows and as stocking changes.

Distribute food across more than one point when a dominant fish controls the first feeding area. This improves access for quieter tankmates without releasing an excessive total ration. Observe every individual in a group; schooling or following the other fish does not prove equal intake, and a subordinate may gradually become thin while the rest remain well fed.

Monitor every individual rather than judging the group by its boldest member. Thin fish may remain near the school while feeding less effectively, especially after a move or a change in hierarchy. If one fish repeatedly misses meals, change food size and delivery, reduce competition, and assess health before assuming another large feeding will solve the problem.

Temperament and Tankmates

Overall temperament: Peaceful. Azurina cyanea is the accepted combination for the species formerly listed as Chromis cyanea. Adults need much more swimming room than their slender juvenile bodies suggest.

Wild aggregations are usually feeding or sheltering associations with far more room to disperse than a home aquarium offers. Do not promise a permanent tightly coordinated school. Individuals may establish a hierarchy, defend a sleeping hole, or become territorial around eggs even when the general temperament toward unrelated fish is peaceful.

The stated minimum is an adult housing recommendation, not a group stocking allowance. Several adults need substantially more swimming volume, multiple refuge areas, and a feeding routine that reaches subordinates. Avoid choosing an arbitrary group size based on the idea that an odd number prevents aggression; observation and usable space matter more.

Choose calm, nonpredatory companions that do not constantly rush the group or dominate every feeding. Large predators and highly territorial damsels can prevent normal open-water activity. Small quiet fishes also need protection from feeding competition, especially where an active group repeatedly clears all food.

Watch for a fish being forced away from shelter, darkening persistently, missing meals, or becoming thin while its companions remain full-bodied. Repeated losses should trigger a review of health, stocking, and hierarchy rather than routine replacement of the weakest individual. Maintain the ability to isolate a bullied or unwell fish.

Reef Compatibility

Reef Safe: Yes.

Healthy coral tissue is not a normal dietary target, so a suitably stocked reef can be appropriate. Reef safe describes the expected relationship with corals and established invertebrates; it does not promise peaceful behavior toward every fish. A territorial damsel can still make a coral-safe community impractical if other fishes cannot feed or use their own shelter.

Copepods, small larvae, and other minute animal foods are part of natural feeding. Established ornamental shrimp, snails, and other larger cleanup animals are generally compatible, while animals small enough to swallow warrant individual assessment. Avoid treating the fish as a guaranteed pest-control agent or expecting the aquarium's microfauna to provide its whole ration.

Secure small coral fragments and keep frequently used shelter entrances clear of delicate tissue. Repeated perching, digging near a nest, or defending an area can disturb livestock without the fish deliberately eating coral. Watch actual interactions after introduction, and separate animals if persistent damage or exclusion develops.

Water Parameters

Temperature: 75–80°F
Specific Gravity: 1.024–1.026
pH: 8.1–8.4
Alkalinity: 8–12 dKH

Maintain stable marine conditions within these practical aquarium ranges. Consistency, good gas exchange, and appropriate biological filtration matter more than repeatedly adjusting the tank to hit one exact number. Control nitrate and organic waste through measured feeding, effective filtration, and regular maintenance.

Match replacement water carefully and avoid sudden changes in temperature or salinity. Check measurements with reliable equipment and observe appetite, respiration, and interactions as well as water tests. Acceptable chemistry alone cannot resolve a social or nutritional problem.

Quarantine new arrivals in a system with suitable shelter and a diet they demonstrably accept. Watch for rapid breathing, skin lesions, unusual withdrawal, or loss of condition before introducing them to the display. Maintain clean transfer equipment and assess each fish rather than assuming that a hardy family is free of disease.

Common Considerations

• Adult Size and Housing: Plan for up to 5.9 inches total length and at least 75 gallons under the conditions described above. Larger communities or groups need additional space and a realistic adult stocking plan.

• Species and Appearance: Azurina cyanea is the accepted combination for the species formerly listed as Chromis cyanea. Adults need much more swimming room than their slender juvenile bodies suggest.

• Food and Condition: Offer small mysis, copepods, cyclops, enriched brine shrimp, and complete small marine pellets. Confirm actual swallowing and review body condition rather than assuming an eager approach or continuous foraging proves adequate nutrition.

• Shelter and Territory: Keep a long open swimming lane beside several retreats; groups need a substantially larger display. Keep entrances accessible and provide several ways for neighboring fish to move out of sight.

• Reef Compatibility: Generally reef safe with suitable livestock, while tiny animal prey may be consumed. Coral compatibility does not guarantee peaceful fish interactions.

• Stable Conditions: Maintain approximately 75–80°F and stable marine water chemistry. Use a secure lid, good gas exchange, and a mature biological filter.