Galaxy Rasbora/Celestial Pearl Danio - Danio Margaritatus

Galaxy Rasbora / Celestial Pearl Danio | A Tiny Jewel for Planted Nano Aquariums

The Celestial Pearl Danio (Danio margaritatus), also widely known as the Galaxy Rasbora, is one of the most breathtakingly beautiful nano fish ever discovered — and its introduction to the aquarium hobby in 2006 caused a genuine sensation. Native to small, heavily vegetated ponds and slow-moving waterways in the Salween River basin of Myanmar, this tiny fish packs an extraordinary amount of detail into a body barely three quarters of an inch long. A deep, midnight blue body scattered with iridescent pearl-white spots, vivid orange-red fins striped with bold black markings, and an almost impossibly jewel-like appearance make the Celestial Pearl Danio one of the most visually stunning freshwater fish available at any size — let alone at nano scale.

In a densely planted aquarium with a large, well-conditioned group, males displaying to one another in a shimmer of blue, pearl, and red is one of the most spectacular sights the nano aquarium hobby has to offer.

Galaxy Rasbora / Celestial Pearl Danio Care Guide

Care at a Glance

• Scientific name: Danio margaritatus
• Also known as: Galaxy Rasbora, Celestial Pearl Danio, CPD, Fireworks Rasbora
• Origin: Salween River basin, Myanmar
• Adult size: up to 0.75 inches (2 cm) — males more intensely coloured than females
• Minimum tank size: 10 gallons — a well-planted nano tank of 10–20 gallons is ideal
• Temperature: 68–79°F (20–26°C) — a cooler water species; best colour and behaviour at the lower end of this range
• pH: 6.5–7.5
• Hardness: moderately soft to moderately hard water
• Best kept in groups of 10 or more
• Lifespan: 3–5 years with good care

Celestial Pearl Danio Tank Setup

A densely planted aquarium with dark substrate, floating plants to diffuse lighting, and gentle filtration suits these fish perfectly — reflecting the calm, heavily vegetated ponds they inhabit in the wild. Java Moss, Bucephalandra, Anubias, and carpet plants all work beautifully and provide the cover and grazing surfaces these fish thrive in. A sponge filter is ideal — it poses no risk to juveniles, provides additional biofilm grazing surfaces, and keeps water flow gentle enough for these small, relatively sedate fish. Stability is key — Celestial Pearl Danios are sensitive to water quality fluctuations and do best in a mature, well-established aquarium.

A tight-fitting lid is recommended — they are capable of jumping through surprisingly small gaps.

Feeding Your Celestial Pearl Danios

Micropredators in the wild, feeding on small invertebrates, zooplankton, and algae. In the aquarium they readily accept high quality micro flake and nano pellet foods, but thrive with regular supplements of appropriately sized frozen or live foods — baby brine shrimp, micro worms, daphnia, and cyclops are all excellent choices and will significantly enhance their colouration and encourage spawning behaviour. Food size matters — crush any standard flake food finely before feeding.

How Many Celestial Pearl Danios Should You Keep?

Groups of 10 or more produce the most natural behaviour and the most impressive display. Males in the presence of other males will display constantly — fanning their fins, deepening their colours, and competing for female attention in a way that is endlessly fascinating to observe. The difference in colour intensity between a lone male and a properly conditioned, displaying male in a group is remarkable.

Celestial Pearl Danio Tank Mates

• Other peaceful nano fish such as Chili Rasboras, Ember Tetras, and small Corydoras
• Pygmy Corydoras and other micro bottom dwellers
• Dwarf shrimp such as Neocaridina — excellent tank mates that share similar water parameter preferences
• Nerite snails and other small snail species
• Avoid any fish larger than 1.5 inches that may view them as food
• Avoid boisterous or fast-moving fish that will outcompete them for food and stress them