Celestial Pearl Danio Size: Adult Growth and Tank Guide

The celestial pearl danio (Celestichthys margaritatus), also known as the galaxy rasbora, is a tiny freshwater fish that rarely exceeds 1 inch (2.5 cm) in length. Adult celestial pearl danio size typically ranges from 0.8 to 1.0 inch (2 to 2.5 cm), making them one of the smallest popular aquarium species. This guide covers their growth rate, tank requirements, and how size affects shoaling and breeding.

Related reading: Discover our full guide on How Long Do Betta Fish Live? Lifespan and Care Guide 2026.

Related reading: Discover our full guide on Black Kuhli Loach: Breeding and Care Guide (2026).

What Is the Celestial Pearl Danio Size?

Adult celestial pearl danios reach a maximum length of about 1 inch (2.5 cm), with most individuals staying between 0.8 and 1.0 inch (2 to 2.5 cm). Males tend to be slightly larger and more colorful than females, displaying a deep blue body with bright orange and white speckles. Females are rounder and often a bit plumper when carrying eggs. Because of their diminutive size, they are ideal for nano tanks and planted aquariums.

Growth Rate and How Big They Get

Celestial pearl danios grow quickly from fry to adult. Hatchlings are barely visible at around 0.1 inch (3 mm) and reach full size in about 3 to 4 months under optimal conditions. Growth depends on water quality, diet, and tank space. In a well-planted tank with regular water changes and a varied diet of micro foods, they will reach their full celestial pearl danio size within the expected timeframe. Stunted growth can occur in overcrowded or poorly maintained tanks, so always provide adequate space.

Celestial Pearl Danio Lifespan

With proper care, celestial pearl danios live for 3 to 5 years. Their lifespan is directly tied to water stability and nutrition. Keeping them in a cycled tank with stable temperatures between 73 and 79°F (23 to 26°C) and soft, slightly acidic water (pH 6.5 to 7.5) helps maximize longevity. Regular partial water changes and a balanced diet of high-quality micro pellets, frozen daphnia, and brine shrimp also contribute to a longer, healthier life.

Tank Size Requirements for Galaxy Rasboras

Because of their small size, celestial pearl danios can live in tanks as small as 5 gallons, but a 10-gallon tank is the recommended minimum for a small shoal of 6 to 8 fish. A 20-gallon long tank offers more swimming space and allows for a larger group, which brings out their natural behavior. The tank should be heavily planted with fine-leaved plants like Java moss, and include driftwood or rocks for cover. A gentle filter and low water flow are essential, as these fish come from slow-moving streams. For a complete setup guide, see our Freshwater Aquarium Setup for Beginners 2026.

Shoal Size and Behavior

Celestial pearl danios are peaceful, shoaling fish that should be kept in groups of at least 6. In smaller groups, they become shy and may hide constantly. A larger shoal of 10 or more encourages confident, active swimming. They are compatible with other small, peaceful species like ember tetras, pygmy corydoras, and small shrimp. Avoid keeping them with larger fish that may see them as food. Their small size also makes them ideal for a 5-gallon pea puffer tank if you want a nano community, though pea puffers can be nippy.

Water Parameters and Care

Maintain water temperatures between 73 and 79°F (23 to 26°C), pH from 6.5 to 7.5, and hardness below 10 dGH. These fish prefer clean, well-filtered water with low nitrates. Perform weekly water changes of 20 to 30% to keep conditions stable. A planted tank with moderate lighting and CO2 injection is not required but helps plants thrive, which in turn provides hiding spots and spawning sites. Feed a varied diet of micro pellets, flakes, and frozen foods like daphnia and cyclops. Avoid overfeeding, as leftover food can pollute the water.

Breeding Celestial Pearl Danios

Breeding celestial pearl danios is relatively easy in a well-planted tank. They are egg scatterers and will spawn among fine-leaved plants like Java moss. To encourage breeding, condition the fish with live foods and perform a slight water temperature drop of a few degrees. After spawning, remove the adults to prevent them from eating the eggs. The eggs hatch in about 24 to 48 hours, and the fry become free-swimming after another 3 to 4 days. Feed the fry infusoria or liquid fry food until they are large enough to accept micro worms.

Common Questions About Celestial Pearl Danio Size

How big do galaxy rasboras get?

Galaxy rasboras are the same species as celestial pearl danios. They reach the same adult size of 0.8 to 1.0 inch (2 to 2.5 cm).

What is the minimum tank size for celestial pearl danios?

A 10-gallon tank is the recommended minimum for a small shoal of 6 to 8 fish. A 5-gallon tank can work for a pair, but a larger group is better for their well-being.

Can celestial pearl danios live with kuhli loaches?

Yes, they can coexist peacefully with kuhli loaches, which are also small and non-aggressive. However, kuhli loaches grow larger, reaching about 3 to 4 inches, so they need more space. See our Black Coolie Loach Care Guide for details.

Where can I buy celestial pearl danios?

You can buy celestial pearl danios from reputable online fish stores, local aquarium shops, or specialty breeders. Always quarantine new fish for at least two weeks before adding them to your main tank.

How many celestial pearl danios should I keep together?

Keep at least 6 to 8 in a group. A larger shoal of 10 or more will make them feel more secure and display natural behavior.

For more aquarium care tips, explore our Aquarium Care category or visit the Fish Tank Guide Hub homepage.