Celestial Pearl Danio Habitat, Behaviour and Breeding Information

Celestial pearl danios are smallish, brightly colored cyprinids that are native to South-east Asian waters. They do not exhibit any form of aggressive behavior, and they love to swim about in a shoal.

They can only grow to a maximum length of about 2.5cm which makes a nano tank ideal for them. They thrive in a tank with a slow flow rate, and their tank should be equipped with plants and other items that make up their hiding spots.

They may be small, but they are never inconsequential within the aquarium. For one, they are pretty colorful and very active. So, there isn’t a dull moment with them in the tank.

Their behavioral pattern, feeding habit, lifestyle and tank mates are extensively discussed in this article. Again, you will get to learn about a few care tips and how you can breed them in the home aquarium.


Scientifically known as Celestichthys margaritatus, the Celestial Pearl Danio or Galaxy Rasbora is an absolutely beautiful pintsized fish which was first revealed by Thai aquarist Kamphol Udomritthiruj in 2006.  Since then, it became very popular and has been given various names.

Habitat and Distribution

This remarkable breed of fish is found in small, shallow and thickly planted ponds in the South East Asia. The species was first discovered ina small plant-laden spring fed pond in Hopong village, Burma. In their natural habitat, you can find Celestial Pearl Danio only in small ponds in the mountainous areas in the villages around Hopong, about 1040m above the sea level in the north of Myanmar. The areas are mostly grassland with abundant sun light filled and rich quality aquatic plants.

The temperature of water where the species is found is 95 degree F in summers and almost freezing during the winters. The place in Hopong from where the fish was discovered was prohibited for the westerners for several years and later many other species where discovered from the same area. Since then, these fishes gave been found in waters linked with the Salween River all over Southern Shan and across the Northern Thailand border.

In 2007, because of overfishing, the species was on the verge of extinction. As the breeding is easy, aquarists got the species bred in tank conditions and fishing in the wild was no more required.

Physical features

You will fall in love with the heavenly charm of these fishes which have exquisite colours all over their body, adorned with pearl like spots on the sides and gorgeous red fins. A group of Celestial Pearl Danio can bring life to any backdrop. What makes these fishes stand out is the coloration of their fins which have two parallel lines of red or orange depending on their sex.


The males of this species are thin and more vibrant in colour. They have an overall deep midnight blue colour; the pearlescent spots are arranged in a series which are clearly visible on the flanks. They also have bright red stripes on the fins and red belly. You can see a unique flash of red stripe on the back of the males which runs all the way from the head to the dorsal fin.


When gravid, the females get rounder and bigger in shape. They are a little light in colour as compared to their male counterparts with golden blue sheen. In females the pearlescent spots aren’t that bright and fins are in a blanched shade of orange. Few females develop an orange colour in the belly. It is said that females develop a dark spot in front of the anal fin on the beginning of spawning.

The fishes in general have a strange body shape with their body length about three times more than their height. The gill plates are almost transparent and you can see the blood vessels through them. It is because of this notable difference in the colours of both males and females that male fishes are given preference while people are buying them for their tanks. However, having all male fishes in the tank can result in a fight between them, so it is advised to have equal proportion of both males and females in the aquarium.


Celestial Pearl Danio has a lifespan of 3-5 years in stable aquariums.

Standard Length

This species of fish is a maximum 1 inch from head to tail in size.

Behaviour and Compatibility

This species of fishes live in groups, so you can keep 6-7 fishes which will keep them active. Very demure and peaceful in nature, these fishes work in harmony with communities that have similarities in their behavior pattern such as Mollies, Killifish, Tetras and Guppies. Having fishes from the same species or origin would also be a great idea as they have almost the same behaviour pattern.

These fishes are said to show great compatibility with Neon Tetras which stay on the upper area of water. Celestial Pearl Danios co-reside with many other species which make them ideal for the peaceful community aquarium.

In case if you decide on having various schooling specie, then your tank would need more water per fish. It is better to have these fishes in company with equal sized species to reduce their shyness. With bigger more aggressive species; Celestial Pearl Danio will get intimidated and outcompeted for food.

Males spend most of the time courting the females and sparring with rival males. The fight between males is nothing to worry about, it is mostly ritualised and the weaker males don’t get harmed if they simply swim away.

However, dominant males can harm weaker one with their teeth if it cannot get away from the fight. If a lot of males are there then it would be advisable to keep them in a bigger tank with lot of plants to avoid fights. By having plants in the tank, the male fishes will have a good hiding place when they are competing for females.

Also, it is noted that these fishes have the tendency to eat juvenile shrimp, so it would be better to have an adult shrimp in the tank.


Galaxy Rasbora fishes are omnivores and prey on smaller critters. In the wild, they eat small spineless species, zooplankton, worms, and small invertebrates. These fishes have small mouth and pharyngeal teeth. In the aquarium, these fishes can eat dry food which is small in size to fit their mouth such as some premium quality flakes. As these like to stay in the bottom of the tank, and rarely swim up to the surface, it would be better to give them food which can sink instead of floating.

You can also, give them small frozen food like daphnia, moina, brine shrimp, small tubifex, small white worms and dried krill which can also help with the coloration of the fins and encourage spawning.

Make sure to give them different types of food instead of repeating the same, which will make them more vibrant. Also, observe the fishes to see if some of them are not getting competed for food. This will help in maintain the longevity of their lives; you can feed the more dominant fishes on one side and shy ones on the other.


Aquarists Pete Liptrot and Paul Dixon of the Bolton Museum Aquarium, U.K were the first to successfully breed these fishes. These fishes spawn every day whether it is in their natural habitat or in the aquarium.

The sex of the fishes is so easy to distinguish that breeding is not difficult at all. Celestial Pearl Danio becomes reproduction at the age of three months. You can simply look for fish which is bigger in size and has a round belly. These female fishes will also have a notable darker colour. If the female fishes are in a nice condition, then they will spawn more often in a nicely-planted aquarium.

In one tank, it is best to introduce a single pair or two males and several females. Although, the higher number of males will increase the risk of egg predation and more competition among each other. For a spawning session, males hover over a clump of plants with their body with a head down angle at the bottom and females swim over to them and initiate the spawning. The pairs do not form any bond and can spawn with multiple mates. For breeding, it is best to use just a single pair in a tank and remove them when spawning is over as they can eat the available eggs.

Nicely conditioned fishes can up to 30 eggs at a time in a single spawning event and they lay eggs where the water movement is low to medium. As discussed previously, feeding them live food will stimulate early spawning.  If you want the females to lay more eggs than you can nourish the aquarium with necessary pH and temperature. There should be fine wool mops or some other fine-leaved plant in the tank.

As the males are ravenous egg eaters and will seek scattered eggs; if you see the eggs, transfer them into a breeding tank. You can use a spawning grate such as a plastic needle-point canvas to separate the eggs from the aggressive males. These eggs will take 72 hours to incubate and later they get into the larval stage where they start swimming.

The newly hatched fry are dark in color and lie at the bottom of the tank. Initially, they do not move much and start swimming only after a couple of days. After some time, they lose their dark colour and get a faded silver tone.

In the breeding tank, feed the fishes micro foods in the beginning like paramecia and after about a week, you can start giving live food such as newly hatched brine shrimp, once the fry are large enough to accept them. The growth of this species is pretty rapid; they take on adult coloration and size in about 10 weeks and reach the adult size at the 14th week. You can start breeding the next generation at 11-12 weeks of age.


It is very important to keep an eye on the males courting females from the beginning as they spend most of the time doing that and fight with other males for potential mates.

You can observe any torn fins or bite marks on the sides of the fishes. This not only harms the fishes but also leads to fin rot. The fin rot can also be caused by poor quality water in the aquarium and there are many ways to prevent it from happening. Make sure to keep the condition of the tank optimal for the fishes by maintaining proper pH and temperature of the water.

You can cure or avoid fin rot by changing water more frequently and using anti-bacterial medications.

Aquarium requirements

In their natural environment, these fishes reside in small ponds which are alkaline and have temperature of above 24 degree C. However, as the water is shallow, the temperature keeps changing and the fishes have got adapted to it.

For an aquarium, the Celestial Pearl Danio is an incredibly timid fish that can become adaptable to a new environment pretty easily. To create a good living arrangement for them, include a lot of plants with a dark substrate in the tank. Lack of plantation will make the fishes edgy and uncomfortable which will lead to them hiding all the time. With large number of plants, these fishes will exhibit their natural behaviour. With a large tank with up to 10 gallons of water, males have plenty of space to move around and avoid fighting. For breeding purpose, do not keep this species with other fishes or shrimps. However, for display, you can introduce other compatible species to these fishes.

Here are some basic requirements for the aquarium in order to keep these fishes:

  • Water should medium hard and a pH around 7 or little high.
  • Regular filtration is required for the water to make sure that it is clean.
  • Tank temperature should be 22-24 degree C, with extremely high temperature, the fishes may die.
  • Provide bright lighting as the fishes originate from sunlit ponds. You can use LED light as long as it doesn’t get too much.
  • You can also use some floating plants as if the aquarium is fully covered with plants, you wouldn’t be able to see the fishes properly.
  • Do not keep large aggressive fishes with this species; you can instead introduce adult shrimps in the tank. The fish is friendly with similar sized species of other fishes.
  • While breeding, you can only have male and female of the same species in the tank.
  • These fish prefer slow or medium moving water.
  • You should also have a lot of rocks, almond leaf litter and driftwood to provide them a natural looking environment.
  • Keep the tank relatively shallow which will mimic the nature of their native habitat.

This is a calm fish breed which is not demanding and can settle in small tanks. Still, it requires a stable condition and some maintenance. Their dynamic colours and grouping nature brings life to any aquarium. As it is the less complicated breed of fishes, it is good for beginners to build knowledge.

Matt Hook

Matt hook has been a passionate aquarist since he was 5 and now he is professional aquarist. Through this blog he plans share his knowledge to beginners. Feel free to contact him if you have any queries.