The celestial pearl danio, also sold as the galaxy rasbora, is a tiny fish described in 2006 from cool, weedy spring pools in Myanmar.
Males show pearl spots over a deep blue body with orange-red fins, making it a popular nano species.
Wild populations were quickly over-collected after discovery, so seek captive-bred stock, which is now widely available and hardier.
It is not difficult to keep but is shy and small, needing a thoughtfully planted tank rather than a busy community.
Housing
A group of six or more suits a planted 40-litre (10-gallon) nano, filtered and held at 20-24C; they prefer cooler water than most tropicals and often need no heater in a warm room.
Dense planting, fine substrate and gentle flow recreate the still, vegetated pools they inhabit.
They are timid and need plenty of cover to feel secure and display.
Avoid strong current and overly warm water, and choose a well-cycled, stable tank, since such small fish are sensitive to swinging parameters in small volumes.
Diet
These are micro-predators that pick tiny invertebrates from plants and substrate.
Offer fine micro-pellets, crushed flake and powdered foods as the base, supplemented generously with frozen or live cyclops, baby brine shrimp, daphnia and microworms.
Feed small amounts once or twice daily, ensuring food is small enough for their minute mouths.
Live and frozen foods bring out their best colour and breeding condition, so rotate them in regularly alongside the dry staple.
Health
Captive-bred celestials are reasonably hardy, but wild-caught fish arrive stressed and prone to parasites and rapid decline.
Ich and fin rot follow chilling or unstable water, and their tiny bodies show illness quickly.
Buy captive-bred stock, acclimatise slowly and quarantine new arrivals.
Keep water stable and on the cool side, perform weekly partial changes, and avoid crowding, as the small volumes of nano tanks punish overstocking and inconsistent maintenance.
Temperament
Peaceful but shy, celestials are not a true tight shoal; males display and spar gently among themselves while staying close to cover.
A larger group spreads out this sparring and encourages confident, colourful behaviour.
They suit calm nano setups with other small, gentle species and shrimp, but are easily bullied or outcompeted by larger, faster fish.
Keep them with equally peaceful tankmates so they feed and display without intimidation.
Intermediate
Intermediate
Intermediate
Intermediate
Intermediate
Intermediate