Galaxy Rasbora Care Guide: Tank Size, Tank Mates & Breeding Tips

Galaxy rasboras pack breathtaking beauty into a fish barely an inch long. They're one of the most sought-after nano fish in the hobby — and for good reason.

Quick Answer: The galaxy rasbora (Celestichthys margaritatus) is a 0.8–1 inch nano fish from Myanmar. It needs a 10+ gallon planted tank with water temps of 72–79°F and pH 6.5–7.5. Keep groups of 8 or more for the best colors and behavior.

What Is the Galaxy Rasbora?

The galaxy rasbora (Celestichthys margaritatus) was only discovered in 2006 — making it one of the newest popular species in the hobby. Scientists found it in shallow, spring-fed pools in Myanmar's Shan Plateau [1].

It's also called the "Celestial Pearl Danio" or CPD. The name fits perfectly: a deep blue-black body covered in pearl-white spots, like a patch of night sky. Vivid red-orange fins with black stripe accents complete the look.

Size and Lifespan

Galaxy rasboras are truly tiny. Adults reach just 0.8–1 inch (2–2.5 cm). Despite their small size, they can live 3–5 years with proper care.

Males are slimmer and more intensely colored. Females are rounder in the belly and slightly paler. Sexing them is easy once fish reach maturity.

Quick Stats at a Glance

Why They Exploded in Popularity

When galaxy rasboras were first exported in 2006, demand was enormous. Prices dropped within months as breeders ramped up. As of May 2026, they're widely available for $3–6 per fish at most local fish stores.

That price point — combined with their stunning appearance — makes them one of the best value fish in the nano tank hobby.

Pro Tip: Buy a group of at least 8 fish at once. Galaxy rasboras show bolder colors and more natural behavior in larger groups. Solo fish or small pairs hide constantly and look washed out.

Tank Setup for Galaxy Rasboras

Galaxy rasboras thrive in densely planted nano tanks with soft, slightly acidic water. A minimum of 10 gallons works for a small group, but a 20-gallon long gives them proper room to shoal.

These fish come from slow-moving, heavily vegetated waters. Replicating that environment is the single biggest factor in their long-term health. Java fern is one of the easiest plants to grow in their preferred conditions.

Water Parameters

These numbers keep galaxy rasboras healthy and colorful:

• Temperature: 72–79°F (22–26°C)
• pH: 6.5–7.5
• Hardness: 2–10 dGH (soft to medium)
• Ammonia/Nitrite: 0 ppm at all times
• Nitrate: Under 20 ppm

Common Myth: "Galaxy rasboras need tropical temperatures above 80°F." Reality: They come from cool, spring-fed mountain pools in Myanmar. Temperatures above 79°F stress them and shorten their lifespan. This is one of the most common mistakes in their care.

Filtration and Flow

Galaxy rasboras are weak swimmers. Use a sponge filter or a hang-on-back filter with a spray bar or flow baffle. Strong currents tire them out and cause chronic stress.

Sponge filters also support beneficial microorganism growth on their surface. Those tiny critters serve as bonus food for fry. This makes sponge filters ideal for both display and breeding setups.

Best Plant Choices

Moderate lighting works best. Heavy shade makes colors look dull. Direct bright light causes hiding behavior all day.

Top plant choices for a galaxy rasbora tank:

• Java fern (Microsorum pteropus)
• Hornwort (Ceratophyllum demersum)
• Flame moss
• Dwarf sagittaria
• Anubias nana

Pro Tip: Use a dark substrate like black sand or fine dark gravel. The contrast makes the fish's white pearl spots and red-orange fins stand out dramatically.

What to Feed Galaxy Rasboras

Galaxy rasboras need small, varied foods — their tiny mouths can't handle standard-sized flake food. According to aquatic nutrition guidelines from the University of Florida IFAS, micro-prey items best match the natural diet of small cyprinids [2].

Good daily staple foods include:

• Micro pellets (0.3–0.5mm size)
• Daphnia (live or frozen)
• Baby brine shrimp (live or frozen)
• Micro worms
• Crushed high-quality flake food

Feeding Schedule

Feed two small meals per day. Only offer what disappears in 2 minutes. Leftover food decays fast in small tanks and spikes ammonia.

Hikari Micro Pellets on Amazon make an excellent daily staple. Supplement with frozen daphnia or live brine shrimp 3–4 times per week for the best coloration.

See Our Top Picks for Nano Fish Food

Check out our top picks for nano fish food on Amazon — all properly sized for small mouths like galaxy rasboras.

How Diet Affects Color

A varied diet directly impacts color intensity. Fish fed live or frozen foods consistently show brighter red-orange fins and more vivid white spots.

Dry-only diets are convenient but produce visibly duller fish. Rotate between 2–3 food types weekly for the strongest coloration.

Best Tank Mates for Galaxy Rasboras

Galaxy rasboras are peaceful and do best with other small, calm species. Avoid anything large enough to fit a galaxy rasbora in its mouth — basically any fish over 2 inches is a potential threat.

Great compatible tank mates include:

• Pygmy corydoras — same size, same water needs
• Honey gouramis — peaceful, small, similarly colorful
• Ember tetras
• Chili rasboras
• Otocinclus catfish
• Amano shrimp — adults are safe; fry may get eaten
• Nerite snails

Fish to Avoid

The Importance of Proper Shoal Size

Galaxy rasboras need their own species around them. A group of 8–12 individuals produces the best display behavior. Males chase and show off for females without causing serious injury.

A mixed-gender shoal in a planted 20-gallon long is one of the most visually rewarding nano tank setups in freshwater fishkeeping.

How to Breed Galaxy Rasboras

Galaxy rasboras are surprisingly easy to breed and make an ideal first breeding project for hobbyists. They scatter eggs among fine plants and spawning moss throughout the day [3].

Setting Up a Breeding Tank

A 5–10 gallon dedicated breeding tank works best. Pack it with java moss or a commercial spawning mop. Keep water slightly cooler than usual: 72–75°F encourages spawning activity.

Condition the pair with live brine shrimp and daphnia for 1–2 weeks before introducing them to the breeding tank. Well-fed females become noticeably rounder with eggs.

Pro Tip: Use a fish spawning mop on Amazon to collect eggs easily. Check and remove it daily during active spawning periods.

Spawning Behavior

Males chase females actively throughout the day. Females deposit 10–30 eggs per session among moss or plant stems. Eggs are small, transparent, and slightly adhesive.

Eggs hatch in 3–4 days at 75°F. Fry are extremely tiny at hatching. They need infusoria or commercial fry food for the first week of free-swimming.

Fry Development Timeline

Fry show adult coloration at roughly 4–6 weeks old. Growth is slow — be patient and maintain pristine water quality throughout.

Common Mistakes Galaxy Rasbora Owners Make

Most galaxy rasbora problems trace back to a handful of avoidable errors. Knowing these upfront prevents most beginner frustration.

Mistake 1: Too Few Fish

Buying only 2–3 fish is the single most common mistake. Small groups are stressed and hide constantly. Keepers often assume the fish are sick — in most cases, they simply need more companions.

Always buy 8 or more from the start. The extra cost is small. The behavioral difference is dramatic and immediate.

Mistake 2: Tank Too Small

Keeping galaxy rasboras in a 5-gallon tank seems logical for such tiny fish. But water quality degrades fast in small volumes with a group of 8+.

A 10-gallon minimum is the real baseline for a small group. A 20-gallon long is strongly recommended for a proper shoal.

Mistake 3: Overfeeding

Galaxy rasboras have tiny digestive systems. Excess food causes ammonia spikes very quickly in smaller tanks. Only offer what disappears in 2 minutes per session.

Common Myth: "Small fish barely need food — once or twice a week is fine." Reality: Galaxy rasboras need two small meals every day. Underfeeding causes stress, competition aggression, and weakened immunity.

Mistake 4: Skipping Quarantine

New fish often carry parasites or velvet disease (Oodinium). This pathogen spreads rapidly and is very difficult to treat in a planted community tank.

Always quarantine new galaxy rasboras for 2–4 weeks before adding them to a display tank. The FishBase species profile for Celestichthys margaritatus lists known pathogens and susceptibility data useful for disease prevention planning.

Ready to get started? Shop nano aquarium starter kits on Amazon to build the perfect galaxy rasbora setup.