The Blue Reef Chromis (Chromis cyaneus) is a peaceful, shimmering blue damselfish that brings motion and color to saltwater aquariums. Often seen schooling above Caribbean reefs, this hardy fish is a favorite for beginners and experienced reef keepers alike. Understanding their needs will help you enjoy their natural behavior and keep them thriving for years.
Natural Behavior and Ideal Tank Setup
In the wild, Blue Reef Chromis form loose shoals over branching corals and rubble zones, darting in and out of cover as they feed on plankton. In captivity, your goal is to recreate that open-water feeling with plenty of safe retreat spaces.
- Tank size: A single Blue Reef Chromis can live in a 30-gallon tank, but a small group of 4–6 does best in 55+ gallons.
- Aquascape: Use a mix of open swimming space and rockwork with caves and ledges for security.
- Water parameters: 1.024–1.026 specific gravity, 76–80°F (24–27°C), pH 8.1–8.4, stable alkalinity and low nutrients.
Because they are active mid-water swimmers, pair them with calm tankmates that won’t outcompete them for food or harass them. They are generally compatible with clownfish, gobies, wrasses, and many reef-safe invertebrates.
For more on building a stable foundation, see our guide on cycling a saltwater aquarium before adding any fish.
Schooling, Stocking, and Compatibility
Blue Reef Chromis are often sold as schooling fish, but their social dynamics can be more complex in aquariums. While they usually coexist peacefully, dominant individuals may occasionally chase weaker ones, especially in cramped or sparsely aquascaped tanks.
How Many Blue Reef Chromis Should You Keep?
- Single fish: Works well if you want a peaceful, active display without social squabbles.
- Small group (4–6): Best in larger, well-structured tanks; spread out aggression with more individuals and hiding spots.
- Odd numbers: Some hobbyists report slightly better dynamics with odd-numbered groups, though this is anecdotal.
Always introduce them together to reduce territorial disputes. Avoid mixing them with highly aggressive damsels or larger predatory fish that may view them as food.
If you’re planning a mixed reef, check out our article on beginner reef-safe fish to find compatible tankmates.
Feeding, Care Tips, and Long-Term Health
Blue Reef Chromis are planktivores, constantly picking small food items from the water column. In the aquarium, they adapt readily to prepared foods.
- Staple diet: High-quality marine pellets and flakes formulated for omnivorous reef fish.
- Supplemental foods: Frozen mysis shrimp, enriched brine shrimp, finely chopped seafood, and copepod-based foods.
- Feeding frequency: 2–3 small meals per day to match their active metabolism.
Hobbyist tip: Feed with the flow pumps on low or pulsing mode so food stays suspended in the water column, mimicking their natural feeding style.
Like many reef fish, they are sensitive to rapid swings in salinity, temperature, and pH. Regular testing, consistent top-offs with RO/DI water, and a steady maintenance schedule are essential. Quarantine new fish for at least 2–4 weeks to watch for marine ich and other parasites before introducing them into your display.
For a deeper dive into ongoing care routines, see our saltwater aquarium maintenance schedule guide.
When kept in stable, clean conditions with proper nutrition, Blue Reef Chromis can live 5–8 years and remain active, colorful members of your reef community.
Conclusion
The Blue Reef Chromis (Chromis cyaneus) offers a blend of beauty, hardiness, and peaceful behavior that suits many saltwater aquariums. By providing ample swimming space, a secure aquascape, compatible tankmates, and a varied diet, you’ll see them display the natural shoaling and mid-water activity that make them so captivating. With thoughtful planning and consistent care, this Caribbean gem can become a long-term highlight of your reef tank.
Sources
- Michael, S. W. (2001). Reef Fishes Volume 1. Microcosm Ltd.
- Sprung, J. (2002). Invertebrates: A Quick Reference Guide. Ricordea Publishing.
- Humann, P., & DeLoach, N. (2002). Reef Fish Identification: Florida, Caribbean, Bahamas. New World Publications.
- General consensus and husbandry practices from experienced marine aquarists and public online reef-keeping communities.
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