Celestial Pearl Danio (galaxy rasbora) care guide

Celestial pearl danio (lat. Danio margaritatus) is a small, bright colored fish, that appeared in tanks not so long ago. Moreover, only in 2006 it became known within the scientific community. This is when it was discovered. It has become popular very fast and like many new species, it got several various names. Besides the main one – celestial pearl danio, it is also called as galaxy rasbora or Microrasbora sp. ‘Galaxy’.

Habitat in the wild

In the wild celestial pearl danio can be encountered only in Myanmar on a small area to the East from Inle lake, more than 1000 m above mean sea level. Its habitat is in Nam Lang and Nam Pawn river basin, Salween river tributaries. Inhabits in shallow and thickly planted lakes.

This species was discovered in August, 2006 in one of the lakes near Hopong village. Europeans quite seldom visited the area where the fish was found and later it become a place where several more new species were discovered.

First the fish was sold under the name Microrasbora Sp. “Galaxy” or “Galaxy Rasbora” in Singapore and soon after that it reached the Great Britain. At first the price was extremely high for such a small fish, but it got lower very fast since quite a lot of species were exported during the next several months.

However, by February, 2007 overfishing of this species has almost led to its extinction and Myanmar department of fisheries officially prohibited export of the celestial pearl danio. Though, aquarists easily got the fish offspring in tank conditions and there was no need to catch this fish in the wild any more.

Only after that 5 more habitats of the galaxy rasbora were discovered. However, if the species were hard to breed, it would be threatened with extinction.

Scientific NameDanio margaritatus
Common NamesCelestial pearl danio; pearl danio; galaxy rasbora; galaxy danio
Range and habitatMyanmar
Size4 cm (1.5 in)
Lifespan2 years
Ease of keepingMedium
Minimum tank size5 gallons
Temperature72-75°F (22-24 °C)
Water hardness5-20 dGH


The size is quite small and it doesn’t exceed 1 inch (2,5 cm). Celestial pearl danio lifespan is quite short, up to 2 years, sometimes a bit longer.

Its dorsal and anal fins are rounded and the fluke is claw-ended. The body color varies from dark blue to black. White, golden or orange spots are scattered all over the body; sometimes they form small stripes. Abdominal fins are transparent in the middle with red edges.

Adult celestial pearl danio male has red abdomen and more bright coloring, while the females are paler with yellowish abdomen. Saturation of the galaxy rasbora coloring varies depending on the mood and its social rank in a school. Besides the brightness of the coloring, you may distinguish the female due to its almost colorless and transparent abdominal fins.

However, only alpha males have full colored dark blue body and bright red fins, while the rest of male may look almost similar to the female.

Even the young males demonstrate vibrant breed colors when playing with females. Unlike, the majority of other representatives of their kind, including celestial pearl danio has a unique way of moving around a tank.

As a rule, they stay in their shelters or focus on looking for food, at that they swim sidewise and incline a bit up or down. When they swim fast to get the food or demonstrate aggression towards a rival male, they quickly open their fins and show their superiority.

Difficulties in keeping

This is a small peaceful fish, that became very popular due to these features. The may reason you may want to get the celestial pearl danio is its ability to live in nano tanks and breed there. Nevertheless, the fish requires stable tank conditions and some experience from its owner, therefore it can’t be recommended for beginners.

Keeping in a tank

Tank decor

This is an incredibly timid small fish, that should be kept in a thickly planted tank with dark substrate. Large number of plants and shelters ensures that the galaxy rasbora demonstrates its natural behavior and makes it less timid.

Floating plants will also be helpful in this respect. If the tank is completely covered with plants, it’ll be rather difficult to observe the fish. Therefore, it’s better to put the plants so that there is some open space in the center of the tank.

The fish is active and friendly, though a very fearful one. So, you mustn’t keep it with large and aggressive fishes, however the fish gets on well with shrimps and it is perfect for thickly planted small tanks.

Tank size

To keep a small number a tank of 5-8 us gallons (20-30 liters) capacity will do. But taking into account size of the fish, it’s better to keep them as a small school of 20-30 species. Smaller number just won’t be seen in a tank.

Water parameters

Here are optimal parameters for keeping: tank water temperature 72-75 °F (22-24 °C), dH 5-20°, pH 6,5-7,5. If the temperature rises to 79 °F (26 °C) the galaxy rasbora doesn’t feel well, at 86 °F (30 °C) it may die.

The fish doesn’t like strong water flow, however moderate filtration and aeration is highly desirable. In general isn’t very demanding and it easily adapts to tank conditions provided with minimal care and proper tank water parameters.

Tank mates

Ember tetra, harlequin rasbora will be perfect tank mates for celestial pearl danio. The galaxy rasbora becomes less shy and fearful in the presence of species of the same size living in the surface and middle water layers. Other small Cyprinidae species from Myanmar such as zebrafish or phoenix rasbora species are also good tank mates.

Due to the fact, that this is a schooling fish even juveniles male compete with each other almost all the time during the day light. The fish may sometimes eat shrimps juveniles, but they don’t eat adult shrimps and they are even afraid of them at times.

Considering the galaxy rasbora shy temper it can’t be kept together with larger and active fishes, that may intimidate them or even take their food and leave them hungry. Surely, it’s impossible to keep them with the fishes that will take celestial pearl danio as food.


In the wild feeds on small spineless species, algae, zooplankton, small worms. In a tank the fish will eagerly eat dry food of proper size, but don’t feed them with just this type of food. Since the fish seldom swims up to the water surface there is no point of giving it some floating food.

Feeding the galaxy rasbora daily with small live and frozen food such as cyclops, brine shrimp, small tubifex will not only make its coloring brighter, but also stimulate the spawning.

Gender differences: male vs female

The female has paler coloring as well as they are larger, then male. They have more rounded and fat abdomen, especially reproductive ones.


Galaxy rasbora becomes reproductive at the age of 3 months, however it’s better to put them into a spawning tank not earlier then in 6 months after the fish was born.

Spawning usually occurs in the middle of small leaved plants and it doesn’t matter where they are located. It can happen both near the tank bottom or near the water surface in the floating plants.

Celestial pearl danio breeding is not difficult. In tanks the fish lays eggs somewhere on the tank plants such as Java moss (Taxiphyllum barbieri) or on some artificial surfaces.

Reproductive females have rounded abdomens and pronounced dark spots on them. When selecting a fish for spawning you can use this feature as an indicator that the galaxy rasbora is ready for spawning. The male selects a place for spawning and strikes a pose 2-3 cm far from the selected area. The fish stays motionless with its head down, body a bit curved, expanded and trembling fins.

It waits for a female to come. Once the female appears, a minute later the couple starts going to the spawning substrate. If other males notice this, they start doing the same. The celestial pearl danio female can lay up to 30 eggs in a time. The eggs incubate from 3 to 4 days at temperature 24-25 °C and they need 4 days more for larvae to start to swim.

During the first three days after hatching the larvae is dark colored and it stays on a solid surface. At this stage it is very hard to see between the larvae and detritus in a tank. Starting from the 4th day the larvae becomes lighter colored and starts to swim; it should be fed with encapsulated brine shrimp.

The galaxy rasbora is not demanding, but it grows very slow. At the age of 7-8 weeks the juvenile’s body starts to look like that of an adult. The juveniles are 1-1.2 cm long at the age of 1.5 months and at 3 months they are of the same size as the adult.

Their coloring starts forming a bit earlier, when they are 2 months old.