Introduction The Celestial Pearl Danio (Danio margaritatus), also known as the Galaxy Rasbora, is a stunning nano fish native to small, heavily vegetated ponds in Myanmar. Despite their small size — typically reaching just 1 inch (2.5 cm) — they pack an incredible amount of color and personality into a tiny package. Their deep blue bodies dotted with iridescent pearl-like spots and vivid red-orange fins make them one of the most visually striking freshwater fish available in the hobby. First discovered in 2006, Celestial Pearl Danios quickly became a favorite among nano aquarium enthusiasts. They are relatively hardy once established, making them a great choice for intermediate fishkeepers who can meet their specific water and habitat requirements. Species Overview Scientific Name: Danio margaritatus Common Names: Celestial Pearl Danio, Galaxy Rasbora Origin: Myanmar (Southeast Asia) Size: Up to 1 inch (2.5 cm) Lifespan: 3–5 years Temperament: Peaceful, slightly shy Diet: Omnivore Care Level: Intermediate Aquarium Setup Tank Size A minimum tank size of 10 gallons is recommended for a small group of Celestial Pearl Danios. Because they are a schooling species, they should be kept in groups of at least 6–8 individuals. A 10–20 gallon tank is ideal for a species-only setup or a carefully curated community. Water Parameters Celestial Pearl Danios thrive in stable, clean water that mimics their native shallow, heavily vegetated ponds. Temperature: 72–80°F (23–26°C) pH: 6.5–7.5 Hardness: 2–10 dKH (soft to moderately hard) Ammonia/Nitrite: 0 ppm Nitrate: Below 20 ppm Perform weekly water changes of 20–30% to maintain water quality. These fish are sensitive to poor water conditions, so a reliable filtration system is essential. Filtration Use a gentle filter — a sponge filter or a hang-on-back filter with a pre-filter sponge over the intake is ideal. Celestial Pearl Danios are small and can be sucked into strong intakes. They also prefer calmer water flow, so avoid powerheads or high-flow filters. Substrate A dark, fine-grained substrate such as black sand or fine gravel works best. Dark substrate helps bring out the fish's vivid colors and mimics their natural environment. It also supports the growth of live plants. Lighting Moderate lighting is preferred. Bright lighting can stress these fish, especially in sparsely planted tanks. If using high-output lighting for plants, ensure there are plenty of shaded areas created by floating plants or dense vegetation. Plants & Décor Heavy planting is key to a successful Celestial Pearl Danio setup. Dense vegetation provides cover, reduces stress, and encourages natural behaviors including spawning. Recommended plants include: Java Moss — excellent for spawning and fry cover Hornwort — fast-growing and great for water quality Dwarf Hairgrass — creates a natural meadow-like foreground Anubias — low-light, easy to maintain Cryptocoryne — mid-ground plant that thrives in similar conditions Floating plants (e.g., Frogbit, Salvinia) — diffuse light and provide surface cover Add driftwood and smooth river stones to complete the natural look and provide additional hiding spots. Diet & Feeding Celestial Pearl Danios are omnivores with small mouths, so food size matters. They do best on a varied diet of: High-quality micro pellets or nano flakes as a staple Frozen or live foods: baby brine shrimp, micro worms, daphnia, and cyclops Feed small amounts 1–2 times daily, only what they can consume in 2–3 minutes. Overfeeding leads to water quality issues, which these fish are particularly sensitive to. Behavior & Social Structure Celestial Pearl Danios are generally peaceful but can display mild intraspecific competition, particularly among males. Males will spar and display to one another, which is natural and rarely results in injury. To minimize aggression, maintain a ratio of 2 females per male and keep groups of 8 or more. They tend to be shy and may hide frequently in sparsely decorated tanks. A well-planted aquarium will encourage them to swim more openly and display their full coloration. Compatible Tank Mates Celestial Pearl Danios are best suited to peaceful nano community tanks. Avoid housing them with larger or aggressive fish that may bully or eat them. Ideal tank mates include: Fish Ember Tetras — similarly sized, peaceful, and share water parameter preferences Chili Rasboras (Boraras brigittae) — excellent nano companions Pygmy Corydoras — peaceful bottom dwellers that won't compete for space Otocinclus Catfish — great algae eaters, very peaceful Sparkling Gourami — compatible temperament and size Endler's Livebearers — active but peaceful; avoid fancy guppies with long fins that may be nipped Neon or Green Neon Tetras — classic nano community fish Invertebrates Neocaridina Shrimp (Cherry Shrimp, Blue Dream, etc.) — safe with adults; shrimp fry may be eaten Caridina Shrimp (Crystal Red, Bee Shrimp) — compatible but require similar soft, slightly acidic water Nerite Snails — excellent algae control, completely peaceful Mystery Snails — safe and useful tank cleaners Fish to Avoid Bettas (may be aggressive toward CPDs) Cichlids of any kind Larger tetras or barbs that may fin-nip or outcompete for food Any fish over 2–3 inches that may view CPDs as prey Breeding Celestial Pearl Danios are egg scatterers and will breed readily in a well-planted aquarium. They do not provide parental care, and adults may eat eggs and fry. To maximize fry survival: Provide dense Java Moss or a spawning mop for eggs to fall into Condition adults with live or frozen foods before breeding Move eggs or fry to a separate rearing tank if possible Feed fry infusoria or commercial fry food until large enough for baby brine shrimp Common Health Issues Ich (White Spot Disease): Caused by temperature fluctuations or stress. Treat with a temperature increase to 82°F and aquarium salt or ich medication. Velvet: A parasitic infection that appears as a gold dust coating. Treat with copper-based medications. Fin Rot: Usually caused by poor water quality. Improve water conditions and treat with antibacterial medication if needed. The best prevention for all diseases is stable water parameters, a clean tank, and a low-stress environment. Conclusion The Celestial Pearl Danio is a jewel of the nano aquarium world. With the right setup — a heavily planted tank, stable water parameters, and peaceful tank mates — these fish will reward you with stunning displays of color and fascinating natural behavior. Whether you're building a dedicated species tank or a thriving nano community, the CPD is an excellent centerpiece fish that never fails to impress. Thank you for reading this guide to Celestial Pearl Danio Husbandry. If you have any questions, email us at scholarlyexotics@gmail.com Shop for Premium Live Schooling/Shoaling Fish through Scholarly Exotics
