10 × Celestial Pearl Danios (Danio margaritatus)

Choose this small danio for a mature planted aquarium

The Celestial Pearl Danio (Danio margaritatus), also known as the Galaxy Rasbora or CPD, is a small freshwater fish in the danionid family from Myanmar. It reaches 2.1 cm maximum standard length, measured to the base of the tail. This social fish suits a keeper who can provide a mature, densely planted aquarium, suitably small food and daily checks on every member of the group.

FishBase records the species from shallow, clear ponds maintained by springs or seepage, with luxuriant submerged vegetation. That natural setting supports a planted layout with cover, broken sightlines and calm feeding areas, but aquarium stability must come from mature filtration and regular maintenance rather than from the fish's tiny body size.

Know the character behind the spots

Blue to blue-green bodies, pearly white to golden spots and red- or orange-marked fins give the fish its familiar celestial appearance. Colour can vary with sex, condition, breeding state and lighting, so use appetite, breathing, swimming and fin condition alongside colour when assessing welfare. A newly settled fish may remain among plants while it becomes accustomed to the aquarium; persistent hiding combined with rapid breathing, damaged fins or refusal of food needs investigation.

The species is social but not simply placid. Rival males spar regularly during daylight hours, and nipped fins are not uncommon within the group. Dense planting and broken sightlines help divide the aquarium into small visual territories, while an open feeding area lets the keeper check that timid fish receive food. These competing needs make the care level intermediate: the water ranges are manageable, but group dynamics, feeding access and stability need active observation.

Galaxy Rasbora is an established aquarium-trade name for the same fish, although Danio margaritatus places it among the danios rather than the true rasboras. Use the complete scientific name when comparing care or compatibility so it is not confused with another fish carrying a similar trade name.

Understand the pack and the commitment before purchase

One purchase supplies one pack of 10 live Celestial Pearl Danios. Ten is Tropical Fish Co's cautious purchase floor for this social species, not a biological optimum or permission to crowd them into a small aquarium. The specialist profile recommends larger groups, ideally 20 or more, when the aquarium has enough footprint, retreat space, filtration and feeding access for the complete adult community.

Sex is guaranteed only when the selected option explicitly states male or female. This 10 × Celestial Pearl Danios listing has no sex-guaranteed option. Colour, body shape and fin markings can offer comparison clues in settled adults, but they do not make this pack a sexed offer.

The gallery images are representative of this type of animal rather than photographs of the exact animal supplied, so colours can look slightly different from the live animal. The number of fish visible in a gallery scene does not change the pack quantity: this offer supplies 10 fish.

Use the decisive planning numbers

The Seriously Fish profile and Tropical Fish Co care guide overlap at 20–26°C, pH 6.5–7.5 and 5–15 dGH.

Start with the 45 × 30 cm footprint, approximately 41 litres in the cited profile, and increase the aquarium's capacity when adding more CPDs or any tank mates. Our complete Celestial Pearl Danio care guide expands the tank, group and water decisions without replacing the need to assess the whole adult stocking plan.

Plan the aquarium around footprint, not small body size

Use an aquarium with a base measuring at least 45 × 30 cm for this group. The Seriously Fish species profile equates that footprint to approximately 41 litres and would not keep a group in anything smaller, because dominant males can be combative despite the fish's small size. Treat 41 litres as a useful starting volume attached to that footprint, not as permission to ignore shape, decor or other residents.

Check the usable base

• Measure inside the aquarium: allow for internal filters, thick hardscape and dense plant bases that reduce usable room.
• Protect horizontal space: a tall aquarium can hold the same litres while offering less useful area for movement and visual territories.
• Count the whole adult community: ten CPDs, additional fish and invertebrates all add waste and competition.
• Keep a separation option: repeated pursuit or exclusion can require one fish to be moved to another suitable, cycled system.

A worked planning example begins with the minimum 45 × 30 cm base and one pack of 10. If tank mates are added, do not treat the original footprint as an unlimited allowance. Reassess adult body size, swimming zone, feeding speed, territorial use and biological load. Increasing litres by choosing a longer aquarium is generally more useful for this decision than adding height alone.

Small aquariums can change quickly when food, waste or temperature fluctuates. The answer is not to reduce the social group until it fits a desktop container. Keep the group intact and choose an aquarium that supports stable filtration, planting, feeding access and routine maintenance.

Before introducing fish, confirm that the base dimensions remain suitable after decor is installed and ammonia and nitrite are zero. Every planned resident must also fit the shared water range for this fish. A mature filter and stable readings matter from the first day; clear-looking water alone is not a cycling test.

Build cover without blocking feeding access

Plant densely enough to break long sightlines while leaving open pockets where food can be seen and eaten. Fine-leaved plants, taller background growth and broad planted areas give nervous fish cover and interrupt repeated pursuit. The layout should create several routes through the aquarium rather than one exposed central lane or a single retreat that a dominant fish can control.

Balance four layout jobs

Floating plants can add overhead cover, but keep sufficient surface movement for gas exchange and leave room to feed and maintain the aquarium. Choose a dark substrate where you can: it is the preferred base for this timid species and makes the pale spots easier to see, although it is not a health treatment. Choose aquarium-safe materials that can be cleaned, and leave out driftwood and oak, beech or almond leaf litter, because the tannins they release are not a feature of this fish's natural waters.

Use gentle, distributed filtration rather than forcing these small fish to remain in a concentrated jet. Gentle does not mean stagnant: water still needs to reach the biological filter and circulate oxygen throughout the aquarium. Adjust the outlet or use a sponge-style unit so the group can choose calmer areas without debris accumulating in dead spots.

Judge a layout by behaviour after the fish have settled. Occasional withdrawal into plants is expected for a timid species. Repeated cornering, one fish being driven from every feeding area, torn fins or sustained refusal to emerge shows that the arrangement is not distributing social pressure effectively. Add or reposition sight breaks only when doing so preserves swimming room, circulation and maintenance access; otherwise use the prepared separation aquarium.

Hold stable water inside the species range

Keep Celestial Pearl Danios at 20–26°C, pH 6.5–7.5 and 5–15 dGH. This is the overlap between the Seriously Fish species profile and Tropical Fish Co's care guide. Choose a stable point within all three ranges that suits every animal in the aquarium; the edges are screening limits, not targets to move between.

Turn a range into one stable plan

One reading held steady inside all three ranges is more useful than letting temperature swing between 20°C and 26°C simply because both endpoints fall inside the range. Apply the same overlap test to every proposed tank mate before combining animals.

Measure temperature with an independent aquarium thermometer, including during the coldest overnight period and warm weather. A thermostatic heater may be needed to prevent drops, while a warm room may mean it runs rarely. Continue monitoring because room heating is not an aquarium thermostat and a heater cannot prevent summer overheating.

Do not chase pH with rapid chemical additions. First understand the source water, aquarium pH and hardness, then choose animals whose ranges genuinely overlap. Our water chemistry guide explains which readings to measure and why, while the water matcher helps compare measured aquarium values with these ranges.

Test again after maintenance, equipment changes or unexplained behavioural changes. Temperature, pH and hardness describe only part of water suitability; ammonia and nitrite must remain at zero, and the nitrate trend must be controlled through stocking, feeding, filtration and water changes.

• If temperature drifts: check the thermometer, heater operation and recent room conditions before changing settings.
• If pH moves unexpectedly: compare tap and aquarium readings and review recent additions or water changes.
• If hardness falls outside 5–15 dGH: plan a stable correction before introducing the fish rather than making an abrupt adjustment during arrival.

Mature the filter and keep ammonia and nitrite at zero

Use a fully established biological filter and keep ammonia and nitrite at zero. The RSPCA explains that biological filtration supports bacteria that convert toxic ammonia into nitrite and then into the safer nitrate. Clear water is not enough: test results show whether the filter is processing waste.

Prepare and mature the aquarium before the pack arrives. If this is your first setup, follow our guide to preparing and maturing a first aquarium, then confirm stable readings before livestock is introduced. Adding ten fish at once increases feeding and waste together, so the filter must be ready for the pack rather than merely running for a few days.

Use a repeatable weekly routine

For general danio maintenance, OATA's group guidance advises testing at least weekly, changing 25% of the water at least once a week, keeping ammonia and nitrite at zero, and preventing nitrate from rising more than 20 mg per litre above the normal tap-water level.

1. Test temperature, ammonia, nitrite and the nitrate trend before maintenance so changes are visible.
2. At least once a week, siphon solid waste while changing 25% of the aquarium water.
3. Treat replacement tap water for chlorine or chloramine before it enters the aquarium.
4. Match replacement conditions closely enough to avoid an abrupt temperature or chemistry change.
5. Check the filter for reduced flow or blockages.
6. When cleaning is needed, rinse filter media lightly in removed aquarium water rather than under the tap.

Clean only lightly so the established bacteria are not lost. Chlorine or chloramine can damage the bacterial population, while excessive cleaning can reduce biological capacity just when ten fish depend on it. After maintenance, check that normal flow has resumed and watch the group for unusual breathing or swimming.

Test outside the weekly schedule whenever feeding increases, a filter slows, fish are added or behaviour changes. If ammonia or nitrite appears, stop treating the result as routine variation: reduce avoidable waste, check filter operation and monitor closely while protecting the fish from further deterioration.

Feed small food where every fish can reach it

Offer suitably small prepared food together with small live or frozen foods such as Daphnia or Artemia. The species diet profile describes small invertebrates, algae and other zooplankton as likely natural foods and advises against an exclusively dry aquarium diet. Build the menu around appropriately sized foods.

Match food to mouth size and feeding zone

• Prepared food: use fine flakes or suitably small granules that can be swallowed without repeated spitting.
• Live or frozen variety: offer small Daphnia, Artemia or similarly sized fare.
• Placement: introduce food where it sinks through the fishes' feeding zone, because this fish rarely rises to the surface and floating products are of little use.
• Access: spread a small ration across more than one open pocket when one fish or a tank mate dominates the first feeding point.

As general danio guidance, feed once a day and offer only what the group can eat within a few minutes. Watch the fish rather than the clock alone: food entering the aquarium is not proof that every CPD has eaten. A useful check is to identify the shyest fish before feeding, follow it through the meal and confirm that it takes several suitable particles without being displaced.

If food remains after the group has stopped feeding, remove it and reduce the next ration. Uneaten material breaks down into waste, adding pressure to a small aquarium and its filter. If every particle disappears instantly but one fish remains thin or excluded, increasing the total ration may only reward the dominant feeders; distribute food more widely or reconsider the tank-mate mix.

Give newly imported fish small live foods such as Daphnia or Artemia as their first diet, and introduce dry and frozen foods once they have settled. Introduce other suitable foods gradually rather than allowing one item to become the entire diet. Biofilm and tiny organisms in a mature planted aquarium can add grazing opportunities, but they do not replace a planned, varied ration.

Check body condition over time. Reduced appetite, weight loss, spitting food, abnormal faeces or one fish consistently missing meals should trigger water tests and closer observation of social pressure and health.

Manage the group as individual fish

Keep at least 10 Celestial Pearl Danios together as Tropical Fish Co's cautious purchase floor. The pack meets that floor, while the specialist profile recommends larger groups, ideally 20 or more, where the aquarium can support them. More fish can spread male rivalry and encourage bolder behaviour, but they also increase waste, food competition and demand for retreat space.

Plan from the adult measurement

FishBase records a maximum standard length of 2.1 cm. Standard length stops at the base of the tail and is not the full tip-to-tip length. Use 2.1 cm consistently for adult-size planning, while remembering that ten small bodies still form a social group with spatial, feeding and filtration needs.

Do not treat one size difference as proof of age, sex or origin. The offer makes no sex guarantee, and visual differences can be affected by condition and breeding state. Manage the fish in front of you by tracking appetite, body condition, fin damage and social access rather than assigning a role from one colour or size difference.

Increasing the group is not an automatic treatment for aggression. First confirm that the aquarium exceeds the base requirement, filtration can handle the added load and planting provides genuinely separate lines of sight. Likewise, reducing the group below ten to create more room can undermine the social plan. When the aquarium cannot support the group safely, move the whole group to a more suitable setup rather than forcing a compromise between space and social needs.

Receive the pack and check health methodically

Arrange for someone to receive the parcel because live fish must not be left unattended. Tropical Fish Co hand-packs live fish in pure oxygen inside an insulated poly box, adding a heat pack when weather conditions call for it, and uses a licensed live-animal courier. Read the current delivery and Live Arrival Guarantee policy before the journey.

Follow the arrival sequence

1. Start filming every delivery while the parcel is still sealed. Continue in one unbroken take as you open it and show the fish still in the bag; this video is needed for any Live Arrival Guarantee claim.
2. Open and inspect the parcel the same day it arrives.
3. Float the bag for 20–30 minutes before releasing the fish.
4. Never pour the bag water into the aquarium.

Once released, observe the group without treating one sign in isolation. Check breathing, balance, swimming, colour, fin position, skin, appetite and whether any fish is being excluded. Compare the whole group: one fish breathing faster, remaining on the bottom or failing to join feeding is more informative than a vague impression that the pack looks quiet.

Use measurements before treatment

If behaviour or appearance changes, test temperature, ammonia, nitrite, the nitrate trend and pH stability. Review recent maintenance, additions, feeding and social conflict. The MSD Veterinary Manual places water quality, history, quarantine and diagnosis at the centre of aquarium-fish investigation.

Do not automatically raise the temperature or add a random medicine. Similar signs can result from water deterioration, transport stress, injury, social pressure, parasites or infection, and treatment depends on the diagnosis, active ingredient, labelled dose, water volume and other animals present.

Seek fish-experienced veterinary help when signs persist, worsen or spread, especially with severe breathing difficulty, ulcers, loss of balance or repeated deaths. OATA's fish-vet finder provides a UK route to appropriate professional help. Keep a record of test results, dates, symptoms and affected fish so a clinician has a useful history.

Screen every tank mate before mixing species

Choose tank mates by adult size, water overlap, feeding speed, swimming behaviour and use of space. Celestial Pearl Danios are likely to be intimidated or outcompeted by larger or more boisterous fish, so avoid animals able to swallow them, repeatedly chase them or consistently take their food first. A species-focused CPD aquarium is a complete and appropriate choice.

Apply the screening rule in order

1. Adult size: reject a candidate capable of swallowing a 2.1 cm standard-length fish.
2. Water: require stable overlap with the shared Seriously Fish and Tropical Fish Co care-guide range of 20–26°C, pH 6.5–7.5 and 5–15 dGH.
3. Feeding speed: reject fish that prevent timid CPDs from reaching small food below the surface.
4. Behaviour: reject persistent chasers or territorial fish that control the CPDs' cover and feeding areas.
5. Space: increase capacity beyond the 45 × 30 cm starting footprint for the complete adult community.

The specialist profile names similarly sized, surface-dwelling fish as potentially helpful for reducing shyness and lists small Myanmar cyprinids such as Celestichthys choprae and members of Microdevario as suitable companions. Treat those examples as candidates that still need individual water, stocking and behaviour checks, not as an automatic shopping list.

Avoid the closely related C. erythromicron because the specialist profile warns that it is probably capable of hybridising with Danio margaritatus. Screen other danios individually; the hybridisation warning applies to this closely related species.

Compatibility remains conditional because individual behaviour and aquarium layout vary. Prepare a suitable, cycled separation space before trying a mixed community. Before trying a mixed community, note the aquarium dimensions, measured temperature, pH and hardness, current residents and their adult sizes, and check every candidate against them.

Protect vulnerable shrimp and manage fin-nipping risk

Do not treat Celestial Pearl Danios as guaranteed shrimp-safe. An adult cherry shrimp may be too large for a CPD to swallow, but shrimplets, eggs and newly moulted shrimp can be vulnerable. Dense plants and moss can reduce encounters; they do not create a fish-proof nursery.

Decide which outcome matters most

Within the CPD group, rival males spar regularly and nipped fins are not uncommon. The profile says this behaviour does not normally extend to tank mates. Distinguish brief display from sustained harassment by watching whether one fish is repeatedly pursued, prevented from feeding or held in a corner.

When nipping occurs, first identify who is chasing whom and where the conflict happens. Check that plants break sightlines, open feeding pockets are not controlled by one fish and the aquarium has enough usable footprint. If rearranging the layout would reduce swimming room or circulation, do not keep adding decor; separate the aggressor or injured fish instead.

Fin damage also needs clean, stable water and close observation. Test ammonia and nitrite immediately, maintain the weekly water-change routine and watch for worsening tissue, altered breathing or loss of appetite. Do not assume all damaged fins result from CPD rivalry when another resident, hard decor or health problem could be involved.

Combine only animals whose adult size, water needs, behaviour and feeding pace all fit, then keep a separation plan ready. Even a combination named in a profile can fail when the aquarium is too small, feeding is uneven or one individual behaves atypically.

Answer the key Celestial Pearl Danio questions

How big do Celestial Pearl Danios get?

They reach 2.1 cm maximum standard length, measured to the base of the tail rather than to its tip. Plan for the complete social group despite the small adult body size.

What size aquarium does Danio margaritatus need?

This fish needs a base measuring at least 45 × 30 cm, approximately 41 litres. Increase capacity for a larger group or tank mates and preserve usable horizontal space after decor is installed.

How many Celestial Pearl Danios should I keep together?

Keep at least 10 as Tropical Fish Co's cautious purchase floor. The specialist profile recommends larger groups, ideally 20 or more, when footprint, planting, filtration and feeding access can support them.

Are Celestial Pearl Danios suitable for beginners?

They suit keepers ready for intermediate care, because a mature planted aquarium, stable water, tiny varied food and close monitoring of sparring and feeding access are required. Keep ammonia and nitrite at zero.

What does Danio margaritatus eat?

Offer suitably small prepared food plus small live or frozen foods such as Daphnia or Artemia once daily. Feed only what is eaten within a few minutes and confirm that every fish receives food.

What temperature and pH does this fish need?

The Seriously Fish profile and Tropical Fish Co care guide overlap at 20–26°C, pH 6.5–7.5 and 5–15 dGH. Choose stable values inside all three ranges that also suit every tank mate.

Is it aggressive or likely to nip fins?

Rival males spar regularly, and nipped fins are not uncommon within the group, although this does not normally extend to tank mates. Use dense planting, broken sightlines and a separation plan for repeated targeting.

Which kinds of fish or invertebrates can it live with?

Consider similarly sized, calm fish with matching water needs and feeding pace; small Myanmar cyprinids such as Celestichthys choprae and Microdevario are named candidates. Avoid fish that swallow, chase or outcompete it, keep Celestichthys erythromicron apart because of hybridisation risk, and treat shrimp young as vulnerable.

How does this fish travel and arrive alive in the UK?

Start filming every delivery while the parcel is still sealed, then continue in one unbroken take as it is opened and the fish are shown still in the bag; this video is needed for any Live Arrival Guarantee claim. The fish are hand-bagged in pure oxygen, placed in an insulated poly box with a heat pack when weather calls for it, and carried by a licensed live-animal courier. Someone must receive the parcel; float the bag for 20–30 minutes before release and never pour bag water into the aquarium.

Check the care and identity references

• FishBase: Danio margaritatus — identity, family, Myanmar distribution, habitat and maximum standard length.
• Seriously Fish: Danio margaritatus — aquarium footprint, water, layout, diet, social behaviour and named compatibility examples.
• OATA: danios and white cloud mountain minnows — general feeding, testing and maintenance guidance.
• RSPCA aquarium environment guidance — biological filtration and waste processing.
• MSD Veterinary Manual — water-quality-led fish-health investigation and diagnosis.
• OATA fish-vet finder — route to fish-experienced veterinary help in the UK.