The celestial pearl danio (Danio margaritatus), often sold as the galaxy rasbora, is a freshwater fish in the danio family. Males have dark blue bodies covered in pale spots that look like stars, with red and black bands in the fins.
Despite the common name “galaxy rasbora,” this fish is a danio, not a rasbora. It stays under an inch long, does best in a group, and suits a planted tank with other small, calm fish.
TABLE OF CONTENTS
Celestial Pearl Danio Facts & Overview
| Scientific name: | Danio margaritatus |
| Common names: | Celestial pearl danio, galaxy rasbora, fireworks rasbora |
| Distribution: | Salween River drainage, Myanmar; reported in northern Thailand |
| Size: | 0.75–1 inch |
| Life expectancy: | 3–5 years |
| Color: | Males steel to deep blue with pale pearl spots and red-and-black banded fins; females duller blue-green with orange fins |
| Diet: | Omnivore; small live and frozen foods plus crushed flake |
| Temperament: | Peaceful |
| Minimum tank size: | 10 gallons (15–20 gallons better) |
| Temperature: | 68–79°F (20–26°C) |
| pH: | 6.5–7.5 |
| Hardness: | 1–15 dGH (soft to moderately hard) |
| Care level: | Moderate |
| Breeding: | Egg scatterer, no parental care |
Distribution
Celestial pearl danios come from the Salween River drainage on the Shan Plateau in Myanmar, with other populations reported in northern Thailand. They live in shallow, clear, slow-moving pools and grassland wetlands, often about a foot deep, thick with aquatic plants.
Heavy collecting for the aquarium trade around 2007 led to fears that the species had been nearly wiped out in the wild. Later surveys found more populations, and the species is not considered under immediate threat. Almost all fish sold today come from commercial breeding.
Adult Size & Lifespan
Adults reach about ¾ to 1 inch (roughly 2 cm) in length. In an aquarium they are commonly reported to live around three to five years.
Availability
Celestial pearl danios are sold at many fish stores and online, usually in groups. Prices change often, so compare a few sellers. Look for fish that are plump, active, and eating, because newly imported or shipped fish can be thin and shy.
Celestial pearl danios are available at these online stores:
Appearance & Behavior
Celestial pearl danios have blue bodies with pearly dots and reddish fins. They are peaceful, but they are small enough to be bullied or outcompeted for food by bigger tank mates.
Colors, Patterns, Fins, and Sex Differences
Celestial pearl danios have a narrow, torpedo-shaped body. Males are slimmer and brighter, with a steel-to-deep blue body, pale spots along the flanks, and red-and-black bands in the fins. Males also have a red belly, and dominant males show the deepest color.
Females are duller, with a blue-green body and fainter spots. Their fins are orange rather than red, and the anal fin is translucent. Some females have an orange or golden belly. Females look noticeably rounder and plumper when they carry eggs.
To tell the sexes apart, look at fin color first and body shape second. Males with red-banded fins are easy to spot; a fish with plain orange fins and a rounder belly is a female.
Typical Behavior
Celestial pearl danios are shoaling fish. A group of at least 8 to 10 is a practical minimum, and larger groups show more natural behavior. Keep more females than males, because males display and spar with each other over the females.
They spend much of their time in the lower and middle parts of the tank, hiding among plants and rocks. At feeding time they come up to the middle and top of the tank. If you only see them at feeding time, the tank probably has too little cover or the light is too bright.
Celestial Pearl Danio Care & Tank Requirements
Celestial pearl danios are not demanding once they are settled, but new fish are shy and can be hard to feed. Dense plants and calm water make the biggest difference.
In the wild they live among thick vegetation, so give them plenty of plants. Don’t use a strong pump or current generator in the tank. Gentle flow from a sponge filter or a filter with a baffled outlet works well.
Habitat and Tank Requirements
A 10-gallon tank is the minimum for a small group, and a 15- to 20-gallon tank is better. A longer tank gives you more floor space and lets you keep a larger group with room for males to keep their distance.
These fish prefer cool to moderate temperatures and do not need a hot tank. Stable, clean water matters more than hitting exact numbers, but avoid the extremes: very acidic, very hard, or warmer than about 80°F.
Cover the filter intake with a sponge so small fish and fry cannot be pulled in. A small, sponge-covered intake also keeps the flow gentle.
Use moderate to subdued lighting. Bright light makes them hide, and floating plants help soften it. Good plants include elodea, egeria, Java fern, bacopa, and rotala. Add floating plants like water lettuce or frogbit for top cover. Rocks add more hiding places.
Choose a sandy substrate or smooth fine gravel. Java moss gives the fish a place to hide and gives fry a place to survive.
Tank Conditions
The celestial pearl danio needs the following tank conditions to thrive:
| Water type: | Freshwater |
| Tank size: | Minimum 10 gallons for a small group of 8–10; 15–20 gallons is better |
| Water temperature: | 68–79°F (low to mid 70s is a safe target; avoid above about 80°F) |
| Substrate: | Fine sand or smooth fine gravel |
| Tank setup: | Subdued lighting, dense plants, floating plants, Java moss, rocks |
| Acidity: | 6.5–7.5 pH |
| Water hardness: | 1–15 dGH (soft to moderately hard) |
| Filter: | Gentle flow; sponge filter or baffled outlet, intake covered with a sponge |
| Water movement: | Slow-moving |
| Water region: | Lower and middle of the tank; comes up to the middle and top at feeding |
| Water heater: | Usually not needed; these fish prefer cool to moderate temperatures |
Published sources give slightly different ranges, so treat the table as a guide. Temperature is commonly given as 68–79°F, with the low-to-mid 70s a safe target. The pH range is 6.5–7.5. Hardness is reported anywhere from very soft to moderately hard (about 1–15 dGH), and the fish do fine in the middle of that range.
Disease
Celestial pearl danios can get common fish diseases, including fin rot and ich. Stress from poor water, bullying, or tank mates that outcompete them for food is the usual trigger.
Signs of illness to watch for:
- Frayed, shortened, or discolored fins (fin rot)
- White salt-like spots on the body or fins (ich)
- Clamped fins, hiding all day, or refusing food
- A thin belly on a fish that has been in the tank for weeks
Fin rot is usually bacterial and follows poor water quality or injury. Start with a partial water change and test ammonia and nitrite. If the fins keep eroding, treat with a medication labeled for bacterial fin rot. Quarantine new fish for two to four weeks to avoid bringing in disease.
Celestial Pearl Danio Tank Mates
Celestial pearl danios are tiny and easily outcompeted, so house them with other small, peaceful fish that like similar water. Avoid anything large, boisterous, or aggressive.
Good tank mates for celestial pearl danios include:
- Other small danios and Microdevario or Boraras rasboras
- Pygmy hatchet fish
- Cherry shrimp (adult shrimp; the danios may eat shrimplets)
- Amano shrimp
- Ember tetras
- Honey or sparkling gourami
- Cory catfish (the smaller species)
- Kuhli loaches
- Snails
Some fish often listed as tank mates need a closer look. Guppies, molly fish, and Endler’s livebearers do best in harder, more alkaline water than celestial pearl danios, and mollies are much larger and more boisterous. Cardinal tetras prefer warmer water. Regular tetras and green tetras can be too active for such a small fish. Other danios and killifish can work, but only in a tank with lots of cover. Avoid keeping celestial pearl danios with the closely related Danio erythromicron (emerald dwarf danio), because the two can hybridize.
Unsuitable tank mates for celestial pearl danios include:
Keeping Celestial Pearl Danios Together
Keep a group of at least 8 to 10, and more if the tank is big enough. A bigger group spreads out male displays so no single fish takes all the pressure.
Watch the male-to-female ratio. In a small tank with few hiding places, the less dominant males get chased by the dominant ones. Aim for more females than males, use dense plants to break up sight lines, and be ready to move a harassed male to another tank.
Diet and Feeding
In nature, celestial pearl danios eat small invertebrates and plant matter. In an aquarium they need small foods, and they do best with live or frozen items fed alongside prepared food. Feed small amounts two to three times a day, and remove any uneaten food after a few minutes so the water stays clean.
Foods that work well:
- Finely crushed dry flakes
- Micro pellets
- Small white worms
- Moina
- Daphnia
- Grindal worms
- Newly hatched brine shrimp
- Finely ground freeze-dried krill
- Frozen cyclops
Newly bought fish often ignore dry food at first. Offer live or frozen daphnia and baby brine shrimp for the first couple of weeks, then mix in prepared food.
Breeding
Celestial pearl danios are among the easier danios to breed. They scatter their eggs and give no parental care, so the adults will eat eggs and fry if they find them. A mature, well-fed group in a planted tank will often spawn on its own.
Each spawning produces only a small number of eggs, usually a dozen or a few dozen, but females spawn often. Fry that hatch in a planted community tank have a decent chance of surviving if there is dense moss.
To raise more fry, set up a breeding tank:
- Use a small tank with Java moss or a spawning mop, plus an air-powered sponge filter.
- Add a male and one or more females, in good condition and fed live foods.
- Remove the adults after a few days or move the eggs, since the adults eat them.
- The eggs hatch in about two to five days, depending on temperature.
- Feed the fry infusoria or other micro foods for the first week, then newly hatched brine shrimp.
Fry grow quickly and reach adult size in roughly three months.
Should You Get a Celestial Pearl Danio for Your Aquarium?
Choose celestial pearl danios if you have a planted tank of 10 gallons or more, want a group of tiny, colorful fish, and can offer live or frozen food. They suit a calm community with other small fish.
Skip them if the tank already holds large, boisterous, or aggressive fish, or if you can only keep a few fish. A group of two or three will not feel secure and the males will fight.
Celestial Pearl Danio FAQs
- Are celestial pearl danios aggressive?
- Is the celestial pearl danio a schooling fish?
- Will celestial pearl danios eat shrimp?
- Where are celestial pearl danios from?
- What do celestial pearl danios eat?
- Are celestial pearl danios fin-nippers?
- How many celestial pearl danios should be kept in a 5-gallon tank?
- How many celestial pearl danios should be kept in a 10-gallon tank?
- Are celestial pearl danios easy to keep?
- How many celestial pearl danios should be kept together?
I have 3 and just ordered 6 more. They are tiny and fun.
I bought the last 4 babies from a lfs and they quarantined well before adding in with some neon tetras. We’ve enjoyed them and I’m looking for to add more. Would like to find a site that has photos of the growth so I can better understand how old they were when purchased.
Have 6 of these with guppies, tetras, discus and clown loaches. Fit in fine, discus leave them alone, no snacking. Great addition to the tank
Thank you for your articles!
We have two groups of celestial danios. The first group of 9 are mostly greenish, with the males being more blue. The second group of 15 is darker overall, and the males are almost black. Striking difference in appearance, although exactly alike in every other way. Two different breeders, we guess. Both have fins more orange than red and both spawn almost daily, usually within an hour of turning the lights on in the morning.
Due to the lower population density, the smaller group does best with actually completing spawning. The larger group contains so many males (6m/9f), they spend most of their time chasing each other off and the time it takes for one of them to finally pin one of the females is much longer and often interrupted. I think an ideal number is no more than about three males to about ten females. Only a small number of females are ripe at any given time and so as they rotate through, any males are concentrated on only the few ready females. As it is, we get plenty of spawning, but it’s a meelee…
They are sporadically available here (Maryland) and you really should get them when they first arrive at the shop. I typically see them look good upon arrival, but they are tiny, probably 1/2″ long and very limited as to what they can eat. As time goes on, the remaining fish in the tank lose condition and are often very skinny after a couple weeks, like they cannot eat most whatever they are being given. I had been feeding our little ones chopped up blackworms and brine shrimp, and ‘First Bites’ powdered food. I had the dark batch about two weeks and when I went past their original tank in the store, I could see the remnants were half the size of ours and stunted-looking.
Because we have corys in the tanks that have learned to follow the spawning celestials around, and because any surviving fry would be at the mercy of the adult celestials, which hunt intensely almost all of the time, we have yet to see a baby celestial. Just as well, the cory population kind of exploded on us and we don’t want even more tanks.
We also have an increasing number of about 50 cherry shrimp that reproduce freely in the community fish tanks and it seems that if the shrimp can get to about 1/4″ long, the celestials don’t bother them. We see this in both celestial tanks. You can see the celestials coming over and sizing them up, but then turning off. When we feed adult brine shrimp to the celestials, they are borderline too big for them. They have to work on one for awhile before they get it down and these brine shrimp are much more ‘feathery’ then the cherry shrimp of the same size.
A quick update (11-23-19):
Our dark batch of celectials have produced several groups of babies with individuals that have survived in a heavily planted 40 gallon breeder tank.
We have had a case of “give and take”, where several barely mobile babies will show up, looking like a hair with eyeballs, then, within a day or two, they’re all gone but one or two. I have a horizontal beech limb in the tank about 2/3rd of the way up toward the surface, with several clumps of various mosses, some well infested with hair algae, spaced along it’s 24″ length and the babies show up in and around the moss. As those one or two survivors grow, we will see more tiny fry appear, then most will disappear again, leaving one or two.
As a result, I currently have 11 fry between 3/8″ long and barely big enough to see, probably at least 4 or 5 age classes. The largest ones are getting their color and are moving about among the adults with impunity. The smallest three have been in there a week and seem to have learned to avoid the adult fish, so they’ll probably make it too.
I have several spawning sites in the 40-B tank; several Java Moss clumps tucked into rock crevices near the bottom, a group of small ‘Wendtii’ crypts planted along a sumberged beech limb lying on the bottom, and a cluster of Java Ferm mounted on a piece of driftwood about 8″ long. The root mat around the convoluted strip of driftwood is very thick and if I had to guess, I’d say most of our survivors came up from that impenetrable tangle.
The odds against survival in a community tank (Celestial Danios, Corydoras, Otocinclus & cherry shrimp)are incredible:
1) Any following males not actually involved in the spawn will quickly grab any loose eggs and look carefully for more.
2) The corydoras I have for cleanup know what spawning time is and will stage themselves at strategic points and eat the eggs as soon as the fish move off. I have larger size gravel in known spawning areas, but the corys are like little vacuum cleaners. I can distract them with blackworms if I need to, but they are pretty persistent.
3) The shrimp, corys and otocinclus constantly search the bottom for anything edible, so most eggs that do happen to make it past the spawing/feeding meelee, as well as fry still working off a yolk sac, get snuffled up. I know the Otos are supposed to be vegetarians, but that is not strictly the case. The shrimp will eat anything and will often catch a blackworm and then fight to keep it.
4) The adult Celestials, most notably the adult females, hunt constantly and with great focus. I have wild daphnia, cyclops, planaria and scuds in the tank and the fish hunt for them, as well as for their own fry. The adult female Celestials literally worm their way through the moss and algae searching for prey.
5) The newly mobilized fry are microscopic and finding food for them can be challenging. I found that the “First Bites” I was recommended is a little too big and they can only eat a very few tiny chips of it. I may have lost some of the early fry because they couldn’t get enough to eat. I have been using a fine powder consisting of krill and spirulina they they eat readily. Once they are a couple weeks old, they can eat more of the ‘First Bites’ and frozen daphnia.
Wow good info. Thanks
Very helpful. Thank you!
This is awesome! Thanks so much!
Put a pair of pearl danios with a single male clown killifish of flagfish
Feeding fry as small as that is problematic. I hard boil an egg then mash the yolk and liquifry it. It can be drip fed from a pipette or by a syringe
Thank you for that information. I’m trying different ways of breeding them. Haven’t had a huge success yet, but I’m learning. I have about 20 fry that I’m babying right now. I feed them powder.
I know this is very old, Ed, but how did the fry end up?
We have a 45 litre tank currently with 3 Platty, 4 Neon Tetra and 2 Danio a couple of Netrite Snail and 4 ghost shrimp, the tetras and danio are pretty hard to tell if they are male or female, but the platty i know i have 2 female and 1 male, i now have 9 platty fry and i was concerned that they would be eaten from reading various articles but they were left alone straight away and are growing at a rapid rate!
Would the celestial be a good addition? I LOVE the danio’s and these are stunning!
I have just bought eight of these beautiful little fish from my local fish shop. I tried to get more females than males, but I think I ended up around 50:50 (although they are tiny and I am long-sighted so can’t be certain!).
I have them in a heavily planted tank, by themselves (might add some shrimp or a nerite snail later) and they are truly beautiful, but still quite shy.
I’ve tried Tetra Min flakes (ignored, even though I crumbled them into tiny pieces) and Tetra microgranules, but no interest in either. Maybe they need more settling in time, though. I have some frozen bloodworms that the mixed tetras in my main tank devour as if they’ve been starved (they definitely haven’t!), but again, no interest.
My lfs is generally very good and the staff both passionate about their fish and knowledgable, so these guys are in great shape despite having been there for a few weeks now. I just have to keep them that way…
Questions: how vital is a pH of >7? Mine is refusing to budge above 6.8-6.9 and I’m anxious it won’t suit them. Other water parameters are spot on and the water is stable at 77 degrees.
I feel like a first-time parent! The anxiety!
Did you ever get you CPD to eat? They can be fussy at first. Mine will go crazy for baby brine shrimp! They also eat eat tiny pellets but takes them a few tries, and only certain brands. They also like frozen blood worms, but I have to chop them up to 1/3-1/4 the size they come in.
I bought 2 a few months ago and was lucky enough to get a Male and female. There are 5 ember tetras in the same 10 gal. tank and some cherry shrimp. I got three eggs out of the moss and raised three babies in a 3 gallon algae covered tank. I fed them powered food until they were a couple weeks old and could eat baby brine shrimp. They are now with their parents and the ember tetras in the 10 gal tank almost grown. It took several months for them to get this big. I was able to get a couple more eggs and raise 2 more babies in a breeder net in the same tank. These two are now growing up in a five gallon tank with some cherry shrimp. Then I got some more eggs and have 6 more in a breeder net in a different tank. They are still tiny. Unfortunately my water is very hard, but they seem to be thriving even though the pH sometimes gets as high as 8.2. I plan on putting all 8 of the newest babies in a separate tank. Now, thanks to your article, I know it should probably be bigger than a 10 gallon. Maybe a 20 long? They have some growing up to do first.
Thanks for the valuable info. I have only been keeping fish a year. Can I put Phoenix Rasboras in the same tank? I just got 12 who are in quarantine.
The CPD’s seem a bit rough, but maybe that is just with each other. They don’t harass the ember tetras. Also I have no idea of the sex of the 11 babies. I hope there are a lot of female, but even when they are tiny fry a couple will break off and “fight.” This might mean those are male. Thank you.
My son bought 9 fish and put them in a 20 gallon, with some white cloud. Damned if the little buggers decided to spawn. We got over 30 fish within a week. He didn’t have the room, and I inherited them. Have had them in a 30 gallon tall, with white clouds, for 3 months, and now have reduced the white clouds, and added 7 platties. My eyes are bad (caterachs sp)so I can’t see the colours, but they have seemed happy enough. I’m here to learn more about them, because I have a Plecko that needs a home where he won’t be harassed. Sounds like eventually I can put him in with the Celestial Pearl Danios, at a higher temperature: 76-77 degrees. Later I’ll buy another 30 gallon long if they get along. BTW I’m getting back into having fish, after 45 years. Things have certainly changed a lot.
I’d added 12 of em to my 13 g (50l) shrimp tank to stop the overbreeding of shrimp. Sadly 2 males were killed by alpha/s? . Now i have better ratio of 6 females to 4 males and they seem more chilled out.
WARNING: they eat only food WHICH FLOAT in the water column so feed flakes but many times small amount or :( small live food
(MY CYCLE OF FEEDING THEM tetramin flakes, microflora (moreless algae), crushed biomax (originally for shrimp) and live daphnia + naturally shrimplets.
BREEDING: they will breed all the time, but they will eat all their fry (need to collect eggs from spawning moss – adjust the temperature for fry to at least 24°C (idn °F) and feed them infusoria or powdered yeast for 4-6 days
they need to be separated from parents till 1 cm +
I have three in a ten gal and they will take care of snail egg clusters. My tank was originally a shrimp tank but the snails were making a lot of waste, so these guys and an assassin snail fixed that. Its nice to have something a little more energetic and the shrimp are more active now.
Looking at getting a few of these for my planted 10gal, thanks for the info! Anyone know if I’d have any trouble keeping a few cherry shrimp as tank mates?
Hey there,
I’ve read that it’s ok to put 80-100 galaxys in 96 L / 21 gal, being a 23 x 16 x 16 inches tank (60 x 40 x 40 cm). Seems absurd, even preposterous to me !
What do you think ?