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Celestial Pearl Danio (Galaxy Rasbora) – Ultimate Care Guide

If you’re looking for an unusual little fish to add to your freshwater aquarium, you may want to consider the Celestial Pearl danio. These beautiful fish were undiscovered until 2006, when a community was found living in just one small area in Hopong, Myanmar. The fishes’ brilliant colors and peaceful temperament immediately made them a hit with hobbyists, especially those who enjoy fish breeding.

But for how long do danios carry eggs, and how do you tell male and female danios apart? That’s what you’ll need to know if you want to breed from your stock.

In this comprehensive guide to Celestial Pearl danio care, we answer those questions and more!

What’s In A Name?

Celestial Pearl Danio

Celestial Pearl danios are fish of many names!

  • Danio margaritatus
  • Fireworks rasbora
  • Microrasbora sp.
  • Galaxy rasbora
  • Pearl danio

All those names can make matters very confusing when you come to look for the species in fish stores or online.

To add to the mystery, the species was originally called Celestichthys margaritatus, which translates as “heavenly fish adorned with pearls.” However, they were later reclassified and renamed Danio margaritatus. The name Galaxy rasbora was given to the fish by hobbyists before the species was officially reclassified, and the popular moniker stuck.

Origins

Celestial Pearl danios are only found in one very small area close to the city of Hopong in Burma to the east of Inle Lake, where the species remained undiscovered until 2006. Unfortunately, thanks to enthusiastic hobbyists clamoring for specimens of these brilliantly colored, peaceful fish, numbers of Celestial Pearl danios in the wild crashed.

children fishing on the river

So badly were numbers decimated by overfishing, that six months after the first specimens appeared in fish stores, the Pearl danio was so rare that it was feared to have become extinct. With no captive breeding programs, all the specimens that were available for sale were wild-caught, and many of the small pools inhabited by the fish were rapidly becoming fished-off.

In 2007, the government of Myanmar intervened, banning the collection and export of wild Celestial Pearl danios. Fortunately, wild danios are extremely prolific breeders, and ponds that appeared to be empty were quickly found to be completely restocked within only a few months.

Today, the Celestial Pearl danio is currently categorized on the IUCN Red List as “decreasing,” although all the specimens that you find for sale these days are captive-bred.

In fact, provided that you give the danios the conditions they prefer, you will most likely be able to raise your own fish successfully in your home aquarium.

Common Name (species) Celestial Pearl Danio, Galaxy Rasbora, Danio margaritatus
Family Cyprinidae
Origin Hopong, Myanmar
Diet Omnivore: Pellets, flakes, frozen brine shrimp, bloodworms, and some live food, including brine shrimp and white worms.
Care Level Easy
Activity Peaceful, shy, and happiest in a school of at least six.
Temperament Peaceful Community
Tank Level All areas, but prefers the middle water column.
Minimum Tank Size Nano tanks, 10-gallon
Temperature Range Tropical 65° to 80° F
Water Hardness dGH 1-5
pH Range 6.5 to 7.5
Filtration/Flow Rate Prefers well-filtered water with a low flow rate.
Breeding Egg scatterer.
Compatibility Peaceful community fish but can be shy. Avoid housing with large, aggressive fish.
OK for Planted Tanks? Yes, prefers a heavily planted tank.

Appearance

The Celestial Pearl danio grows to around 1 to 1.5 inches in length, having a plump body and a blunt nose.

Male fish are typically brighter in color than females with a brilliant blue body and brightly colored finnage. Males are covered with a scattering of pretty, pearly spots. In comparison, females are a dull blue-green color with transparent fins. In both sexes, the gills are transparent, allowing the vibrant red coloration to show through. Male fish have fins with two black parallel lines sandwiching a scarlet center. In females, that pattern is only present on the dorsal and caudal fins, and sometimes on the anal fin.

When in spawning condition, the male Celestial Pearl danio has a bright red underbelly with his body becoming a darker, brighter color so that the pearlized spots are more highlighted. Females develop a black anal spot when in breeding condition.

Juvenile fish have a striped pattern that eventually changes to become the pearly spotted adult markings. That can make it difficult to determine whether the young fish you buy are boys or girls, which is a nuisance if you want to establish a breeding community.

Activity Level/Temperament

Celestial Pearl danios are peaceful fishes that won’t trouble any of their tankmates. These dainty little creatures are rather shy and tend to hide away in caves or amongst lush planting, sometimes to escape harassment by other fish or to get away from overly bright lighting.

These fish spend much of their time cruising in the middle region of the water column, occasionally exploring the substrate or darting up to the surface. Galaxy rasboras are typically a shoaling fish, spending much of their time journeying around their environment in a school.

Although you can keep pairs of these danios, they are much happier and more confident when kept in groups of five or six individuals. In fact, if you keep a single-species tank containing a large group of Celestial Pearl danios, you’ll get to enjoy a glorious display of colorful activity, especially when the fish begin to spawn and their colors become even more dazzling and vibrant.

Compatibility And Tankmates

Celestial Pearl danios are delightful small tropical fishes that do extremely well in a peaceful community tank. Large or very aggressive species should be avoided, as the danios are shy fish that are easily intimidated, and they will become withdrawn and stressed if harassed by other tankmates.

Aquarium with cichlids fish from lake malawi

Pearl danios are related to the Danio erythromicron, and they have virtually identical care requirements. So, if you want a large tank with plenty of activity and vibrant colors, a small school of those fish makes a nice mix with an equal number of Celestial Pearl danios. Another good choice of small, brightly colored fish that can make the perfect addition to a community of small fish is Endler’s livebearers.

If you wanted to add a little more interest to your display without introducing more fish, you might want to consider adding a few small snails and shrimp. These invertebrates are peaceful, harmless creatures that can also act as an efficient clean-up crew, eating leftover food, algae, and picking up detritus from the substrate.

Pearl danios generally cannot live with betta fish, as their bright colors can sometimes trigger aggressive behavior in the territorial betta.

Feeding

In its wild environment, the Celestial Pearl danio lives in small ponds that are created by water rising from seeping groundwater or small springs. The fish are omnivorous, taking small invertebrate creatures and insect larvae, as well as eating plant matter and algae. In the home aquarium, it’s important to replicate the fish’s wild diet as closely as possible.

What To feed

These fish are pretty easy to please when it comes to food, thriving on a staple diet of good quality, tropical omnivore flakes or micro-pellets. You can add variety to the diet by including frozen foods, including brine shrimp, mosquito larvae, and bloodworms.

Frozen bloodworm for feeding aquarium fish and crabs.

Frequency

As with all fish, you should never overfeed your danios. Overfeeding can cause health problems, and uneaten food will simply fall down into the substrate where it will decompose, polluting the water.

Feed the fish twice daily, offering them just what they will eat in two minutes.

What Not To feed

Although you can feed live foods, such as daphnia, brine shrimp, and bloodworms, you should be sure to use a reputable supplier. Never take foods from the wild environment, as you could inadvertently introduce disease or parasites to the tank. For that reason, I prefer to use frozen foods for my fish, rather than risk accidentally bringing problems into my aquariums.

Although Celestial Pearl danios will eat freeze-dried foods, we recommend that you soak the food in a little tank water before offering it to your fish. That way, the food will rehydrate so that it doesn’t swell inside the fish on contact with moisture, which could cause digestive problems.

Tank Requirements

One of the primary killers of captive fish is stress. Stress weakens the fish’s immune system, which leaves the creature more susceptible to attack by parasites and common fish diseases. Providing the Celestial Pearl danio with their preferred living conditions can go a long way to preventing stress, resulting in healthier, happier fish.

Tank Size

Aquarium with fishes on dark background

Celestial Pearl danios are small fish, and they can be kept successfully in nano tanks. You can comfortably house a small school of six to ten fishes in a nano aquarium or 10-gallon tank.

However, if you want to introduce more fish in the future or keep some of your home-bred danios, you will need a bigger tank. Ideally, you should allow one gallon of water per inch of fish, preferably more than that if you have lots of decorations and plants in your tank that take up swimming space.

As this is a shoaling species, it’s best to choose a tank that’s long in dimension rather than tall so that the fish have plenty of open water swimming space for schooling. Also, the surface area of a long tank is greater than that of a round or tall one, providing better water oxygenation, which is important for these fish.

Tank Setup

The best way to keep your Pearl danios healthy and happy is to provide them with a home-from-home setting in the aquarium. The closer you can get to the danio’s wild environment, the happier they will be. Also, you’ll get to enjoy the fishes’ natural behavior, their colors will be brighter, and they will be more likely to spawn.

Substrate

Sand dunes isolated on white background

Fine gravel or sand is the best substrate to use for Celestial Pearl danios. To make the most of the fishes’ bright colors, choose a dark-colored substrate. Also, as the fish are rather shy, a dark substrate will make them easier to view even if they’re hiding amongst plants.

Decorations

The danio’s natural habitat includes lots of pebbles and driftwood, so you should use that in your aquascaping. As a shy species, the Galaxy rasbora can easily become stressed, so having somewhere to hide and take refuge is extremely important. For that reason, rocky overhangs and caves also make a good addition to the tank.

Planting

In their wild home, Galaxy rasboras live in very heavily planted ponds. The plants provide the fish with shelter and safety, as well as harboring small invertebrates and insect larvae on which the fish feed.

In the captive environment, you must use lots of lush plants to recreate that crucial safety net for the fish. Low-growing, sprawling species are a great choice, together with taller plants that can provide cover in the mid-range of the water column.

Beautiful planted tropical freshwater aquarium with fishes. Aquascape.

Remember, if your fish feel safe and secure, they won’t succumb to the effects of stress. Also, the more confident the fish feel, the more you will see of them as they will come out to explore and forage, rather than remaining hidden, so don’t skimp on plants.

Setting Up The Tank

First of all, assemble everything that you’ll need:

Now you can get the tank set up:

Asian women set the fish tank

  1. Begin by washing the substrate through under running water to get rid of any dust and debris, Add the substrate to the tank to a depth of around two inches.
  2. Place the filter unit and heater in the tank, but don’t switch them on yet.
  3. Fill the tank with tap water to a few inches short of the fill line to allow for water displacement when you add your decorations and plants. I always place an upturned saucer on the substrate and pour the water over it so that the water doesn’t displace the gravel or sand beneath.
    If you need to cycle the aquarium before adding fish, don’t add dechlorinator to the tap water. The beneficial bacteria that you’re cultivating in the biological filtration media need ammonia to consume to kick off the nitrogen cycle.
  4. Rinse your decorations to get rid of any dust, and add them to the tank.
  5. Choose a selection of plants, remove any damaged stems and dead leaves, and add the plants to the setup, following the supplier’s planting guidelines.
  6. Now, you need to cycle the tank before you add your fish. Turn on the filtration system and the heater, and allow the tank to cycle for at least ten days before you add your fish.
    Before introducing fish to the tank, test the water using an aquarium water testing kit to make sure that ammonia and nitrite levels are zero, and nitrates are below 20ppm (parts per million)

Habitat Requirements

Filtration

Aquarium equipment. External Aquarium Fish Tank Canister Filter. Vector illustration. The scheme of the external aquarium bio filter. – stock illustration

The Celestial Pearl danio inhabits clear, tropical, fresh water that comes from seeping groundwater or underground springs. That means you’ll need an efficient filtration system that will keep the tank water clean and free from ammonia, nitrites, and nitrate.

These fish live in ponds where there is little to no current, aside from the gentle movement that’s generated by water flowing into the pond from a spring or upward from the water table. So, although the water in your aquarium should be well-oxygenated, you don’t need an air stone or a very powerful pump that produces a strong flow. If necessary, buffer the flow by directing it at decorations or planting.

Water Parameters

Galaxy rasboras are pretty easy to keep, provided that you give them their preferred water conditions.

Water Temperature

Pearl danios can tolerate a broad range of water temperatures, ranging from as low as 65° Fahrenheit right up to 80° Fahrenheit, which is useful if you want to keep other species in the same tank. However, the ideal water temperature for the Celestial Pearl danio is in the mid-70s Fahrenheit.

Although these fish are tolerant of a wide range of water temperatures, it’s essential that the temperature doesn’t change suddenly. All fish are susceptible to temperature shock, and a sudden plunge or increase in cold or warmth can be extremely dangerous. For that reason, be sure to use a good quality aquarium thermometer so that you can monitor the water temperature.

Water Hardness And pH Range

close up image of underwater landscape nature style aquarium tank with a variety of aquatic plants inside.

The water hardness should be between 1 and 5 dGH, and the pH range should be 6.5 to 7.5.

Lighting

These fish prefer medium lighting levels, hiding away from very bright light.

Tank Maintenance

Once you’ve set up your tank and added your fish, you’ll need to keep the environment clean and healthy for them. That means carrying out partial water changes each week to reduce nitrate levels, cleaning and periodically replacing filter media as necessary, and maintaining the plants.

Most captive tropical fish mortality and disease are caused by poor tank maintenance, unsanitary water conditions, incorrect feeding, and stress.

Bottom line: keep the tank clean, the water conditions correct, and feed your fish properly!

Health And Disease

Celestial Pearl danios are generally healthy fishes, although they can be susceptible to a few common diseases of tropical fish.

Signs Of Good Health

These little fishes are generally lively and active, preferring to school around the mid-level of the water column. You’ll also observe them sheltering among the plants or hiding beneath overhangs or in caves. Provided that behavior is not as the result of harassment from larger tankmates, you need not be concerned.

Healthy danios have a good appetite, always appearing at feeding time to grab their share of whatever’s on the menu. The fish should appear slightly plump, and their colors should be bright and vivid.

Celestial Pearl danios generally have a lifespan of around three to five years.

Red Flags

If you notice that your fish appear lethargic and have a poor appetite, that can be a sign that there’s trouble brewing. Also, look out for fish that don’t shoal with their tank mates or spend a lot of time resting on the substrate or hanging at the water surface.

Flicking against the substrate or tank decorations may indicate that the fish are being attacked by parasites. Faded colors, ulcerated patches on the skin, ragged fins, reddened gills, lumps, and swellings can all be signs of disease.

Common Health Issues And Treatment

Health Issue Symptoms or Causes Suggested Action
Ich (White Spot Disease)
Ich is a parasitic disease that’s caused by Ichthyophthirius multifiliis, a protozoan parasite. Fish rubs against the substrate, rapid respirations, a rash of tiny white spots on the body, fins, and gills. Treat the whole tank. The parasite lives in the water, isolating individual fish is not effective. Raise water temperature to 82° F for three days, and treat water with an over-the-counter remedy.
Fin rot Fin rot is caused by bacteria, namely, Pseudomonas, Aeromonas, or Vibrio. Fins appear frayed and ragged with reddening at the base. Use a proprietary water treatment and improve water quality.
Fungal infections Discoloration of eyes, white cottony growth. Quarantine fish; treat with an antifungal remedy as directed.
Bacterial infections Cloudy eyes, reddening of the skin, ulcers. Quarantine fish; treat with an antibacterial remedy as directed.

Breeding

Celestial Pearl danios are extremely easy to breed in captivity. The ideal situation is to keep the fish in a species-only tank so that you can allow nature to take its course. Provided that tank conditions are suitable, the fish will spawn naturally without intervention from you. The downside of taking that approach is that the parents and other members of the school will readily eat the eggs and fry.

Spawning Tank

For that reason, it’s best to set up a separate breeding tank so that you can remove the adult fish as soon as the eggs have been deposited.

Celestial Pearl danios are egg-scatterers, so make sure that the spawning tank is set up with plenty of dense planting, clumps of moss, or spawning mops on which the eggs can be deposited. After around 28 to 36 hours, the fry hatches. The tiny fry needs a suitably miniature food source, and they will happily feed on the micro-organisms and green algae that are growing in the tank until the tiny babies are large enough to take bigger food items.

The fry grows and matures quickly over the three months after hatching. As the juveniles grow, you can feed them crushed flake, baby brine shrimp, and micro-worms. If you have sufficient space and the time, you can raise your own brine shrimp and micro-worms, using a farming kit.

Availability

man holding card while typing on his laptop

You can find Celestial Pearl danios in most good fish stores or through online dealers. The fish are produced in quite large numbers by commercial breeders these days, so you can typically buy one fish for around $4 or $5. Often, you can get a discount if you buy a group of specimens.

Product Recommendations

Here’s a list of supplies that you’ll need if you want to set up a Celestial Pearl Danio tank.

  • Aquarium (minimum size 10-gallons)
  • Filtration system
  • Heater
  • Water conditioner
  • Lighting
  • High-quality tropical flake food
  • Selection of frozen foods
  • Dark-colored substrate
  • Rocks, pebbles, driftwood
  • Books on fishkeeping
  • Fishnet
  • Aquarium thermometer
  • Aquarium vacuum or siphon cleaner
  • Algae magnet

Final Thoughts

Celestial Pearl Danio

We hope you found our guide to keeping the Celestial Pearl danio helpful. Please let us know what you think in the comments box below, and don’t forget to share the article if you enjoyed it.

These beautiful little fish were once hard to find, but now you can obtain a school of them to add to your tank relatively easily. Be sure to provide a well-planted aquarium with lots of hiding places so that these shy fishes feel safe and secure. Make sure that the water conditions in the tank are suitable for the species, keep the environment clean and healthy, and you can enjoy these brilliant, swimming gems for many years.

Check out our infographic and don’t forget to share!

Celestial Pearl Danio (Galaxy Rasbora) - Ultimate Care Guide - infographic

Alison Page has been an avid fish keeper for over 35 years and has owned many different species of freshwater tropical fish including bettas. Currently Alison has two large freshwater tanks. The first tank has two huge fancy goldfish who are almost ten years old and still looking as good as ever. In the other, she has a happy community of tiger barbs, green tiger barbs, corydoras catfish, platys, and mollies.

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