Setting Up the Perfect Aquarium for Celestial Pearl Danios

The Celestial Pearl Danio (Danio margaritatus), also known as Galaxy Rasbora or simply CPD is a small, bright colored fish, that appeared the aquarium trade not so long ago. Moreover, only in 2006 it became known within the scientific community. This is when it was discovered. Overall, the Celestial Pearl Danio is a captivating fish species that can bring beauty and tranquility to a well-maintained aquarium. Their vibrant colors and peaceful nature make them a popular choice among fishkeepers.

Habitat in the wild

It belongs to the family Cyprinidae and the genus Danio. The scientific name for this fish is Danio margaritatus.

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. Due to its small natural range and the increasing popularity of the species in the aquarium trade, the population in the wild has faced threats from habitat degradation and overcollection. In response to these concerns, efforts were being made to study and conserve the species, including the establishment of protected areas and captive breeding programs.

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.



Despite its small size, the Celestial Pearl Danio is known for its vibrant colors and attractive appearance, which contribute to its popularity among fishkeepers. 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.


How big do celestial pearl danios get?

The size is quite small and it doesn’t exceed 1 centimeters (0.8 inches) in length. This makes it one of the smaller fish species commonly kept in aquariums.


How long do celestial pearl danios live?

Celestial pearl danio lifespan is quite short, up to 2 years. However, with proper care and optimal conditions, they can sometimes live up to 3 years or even longer. It’s important to note that individual lifespan can vary depending on various factors such as water quality, diet, genetics, and overall care provided.

Scientific NameDanio margaritatus
Common NamesCelestial Pearl Danio, Galaxy Rasbora, Celestial Pearlfish, galaxy danio
Native RangeMyanmar (formerly Burma) in Southeast Asia
HabitatShallow, slow-moving streams and ponds
Maximum SizeUp to 2 centimeters (0.8 inches) in length
Body ShapeSlender and elongated with a slightly compressed body
ColorationMetallic blue-green body with vibrant red and white markings
FinsDorsal and anal fins are elongated, while the caudal fin is forked
TemperamentGenerally peaceful, but may display aggression during breeding
Water ParametersTemperature: 22-26°C (72-79°F), pH: 6.5-7.5, water hardness: 5-15 dGH
FeedingOmnivorous, will accept a variety of small foods, including flakes, pellets, and live/frozen foods
BreedingEgg scatterers, breed in dense vegetation with a preferred water temperature around 24°C (75°F)
Conservation StatusSpecies of concern, subject to habitat degradation and overcollection

Pearl danio vs celestial pearl danio

The terms “Pearl Danio” and “Celestial Pearl Danio” are sometimes used interchangeably or confused with each other. However, there are actually two distinct species of fish referred to by these names.

Here’s a comparison table highlighting some key differences between the Pearl Danio (Danio albolineatus) and the Celestial Pearl Danio (Danio margaritatus):

CharacteristicPearl Danio (Danio albolineatus)Celestial Pearl Danio (Danio margaritatus)
Common NamesPearl DanioCelestial Pearl Danio, Galaxy Rasbora
Native RangeSumatra, Myanmar, and Thailand and VietnamMyanmar (formerly Burma)
Adult SizeUp to 2.6 inches (6.5 cm)Up to 2 centimeters (0.8 inches)
Body ColorSilver body and two light yellow/white or blue/red stripes. It has an iridescent look.Metallic blue-green with red and white markings
Water ParametersTemperature: 68–77 °F (20–25 °C), pH: 6.0-8.0Temperature: 22-26°C (72-79°F), pH: 6.5-7.5
Water HardnessSoft to moderately hard (5-19 dGH)Soft to moderately hard (5-15 dGH)
CompatibilityPeaceful community fishPeaceful community fish

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

Celestial Pearl Danios are small fish that do not require a large tank. To keep a small number a tank of 10 gallons (38 liters) or larger would be suitable for a small group of Celestial Pearl Danios.

Are galaxy rasboras schooling fish? How many galaxy rasboras should be kept together?

Keep in mind that while Celestial Pearl Danios are small, they are social fish that thrive in groups. It is recommended to keep them in a group of at least six individuals, but ideally, a larger group is even better. A group of 10 to 15 Celestial Pearl Danios would provide a more natural and dynamic social environment for these fish. 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. You could consider a tank with a minimum size of 40 to 50 gallons (151 to 189 liters) for a group of 30 individuals. This would provide ample swimming space and allow the fish to exhibit their natural behaviors.

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. It’s important to maintain stable water conditions within these ranges to ensure the health and well-being of the fish. Sudden fluctuations or extreme values outside of their preferred range can cause stress and negatively impact their overall health.

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.

While they generally get along well with other peaceful community fish, there are some tank mates that may not be suitable due to differences in size, temperament, or water parameter requirements. 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.

Here are a few examples of potentially inappropriate tank mates for Celestial Pearl Danios:

  1. Large predatory fish: Examples include larger cichlids like Oscars, predatory catfish species like Redtail Catfish, or aggressive species. These fish may see the smaller Celestial Pearl Danios as prey or exhibit aggressive behavior towards them.
  2. Fin-nipping species: Certain fish species, such as Tiger Barbs, Serpae Tetras, or Red Eye Tetras, are known to nip at the fins of other fish. Celestial Pearl Danios, with their delicate fins, may be susceptible to fin nipping and stress from these types of tank mates.
  3. Slow-moving or long-finned fish: Slow-moving fish like Fancy Goldfish or long-finned varieties of Betta fish (such as Halfmoon or Crowntail) may not be suitable tank mates for Celestial Pearl Danios. The active nature of the danios may cause stress to these slower or more delicate fish.


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.

Celestial Pearl Danios readily accept high-quality dry foods like flakes or pellets designed for small tropical fish. Look for products that offer a balanced diet and include a variety of ingredients. Remember to feed them in small portions multiple times a day, rather than one large meal, to mimic their feeding habits in nature. This will help prevent overeating and maintain good water quality in the aquarium.

Gender differences: male vs female

Distinguishing between male and female Celestial Pearl Danios (Danio margaritatus) can be challenging, especially outside of breeding conditions.

However, there are a few subtle differences that can help identify males and females:

  1. Size and Body Shape: Males tend to be slightly smaller and slimmer compared to females. Females, especially when mature and ready to spawn, can have a rounder and more robust body shape.
  2. Coloration: During breeding conditions, males typically exhibit more vibrant and intense coloration than females. Males may display brighter red or orange hues on their bodies, while females may appear more subdued.
  3. Fins: The dorsal fin of male Celestial Pearl Danios is usually more elongated and pointed compared to the females, which may have a shorter and rounder dorsal fin. However, this distinction is not always prominent or easy to discern.
  4. Behavior: During breeding, males may become more territorial and display more intense chasing and courtship behavior towards females. However, this behavior can be temporary and may not be observed in all individuals or all the time.

It’s important to note that these differences may not be easily noticeable or consistent in all individuals. The most reliable method to determine the sex of Celestial Pearl Danios is by observing their behavior during breeding.


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.