Celestial Pearl Danio (Danio margaritatus)

Danio margaritatus, the Celestial Pearl Danio (originally described as 'Galaxy Rasbora' when first described to science in 2006), is one of the most exciting aquarium fish discoveries in modern times. When photographs of this tiny, jewel-like fish from Myanmar first circulated on internet forums in 2006, demand was so explosive that collection pressure temporarily threatened wild populations before sustainable collection practices were established.

The fish is extraordinary for its size (1.5–2 cm): a deep blue to navy body densely covered in white to cream pearlescent spots that seem to glow — giving the impression of a miniature galaxy. The dorsal, anal, and caudal fins display vivid orange-red with black striping, particularly vivid in males. The combination of spotted body and patterned fins makes this one of the most exquisitely detailed micro-fish in the hobby.

Native to small, shallow, isolated highland ponds and rice paddies in the Salween River drainage in Shan State, Myanmar, the Celestial Pearl Danio inhabits clear, well-planted, cool waters over muddy or silty substrates. The ponds are densely vegetated with aquatic plants — this influence is reflected in the species' preference for planted aquariums.

Despite its delicate appearance, D. margaritatus is a relatively hardy nano fish once established, adapting to a reasonable range of water conditions. Males are territorial toward each other but peaceful with all other species.

Tank Setup: A 30–40 litre nano planted aquarium for a group of ten. Dense planting with fine-leaved plants (Java moss, Anacharis, Microsorum, Rotala), open mid-water clearing, dark fine substrate, and gentle sponge or canister filtration with minimal flow. Floating plants appreciated for surface cover.

Water Parameters: Temperature 20–25°C; pH 6.5–7.5; GH 5–15 °dH; KH 3–8 °dH. Prefer moderately soft to moderately hard, cool to warm water. Avoid very high temperatures — prefer 22–24°C.

Feeding: Omnivore. Feed micro pellets, crushed flake, frozen baby brine shrimp, Daphnia nauplii, micro worms. Small mouths require tiny food particles. Feed twice daily.

Tank Mates: With other peaceful nano species only: Ember Tetras, small Boraras, Pygmy Corydoras, Otocinclus, peaceful dwarf shrimp. Males are territorial toward each other but entirely peaceful with other species. Keep one male per small territory or use large groups (12+) to distribute aggression.

Behaviour: Males establish small territories within the planted tank and court females with vivid fin displays. Loose schooling but not a tight schooler like Neon Tetras. Active and visible when comfortable in a well-planted setup.

Health: Hardy for a micro fish once established. Sensitive to poor water quality. Avoid ammonia and nitrite spikes. Weekly 20% water changes. Do not keep in very hard or very soft water extremes.