Galaxy Rasbora – Celestichthys margaritatus

The Galaxy Rasbora, also known as Celestichthys margaritatus or Celestial Pearl Danio, is one of the most spectacular nano fish in the aquarium hobby. Its intense colors, gentle behavior and small size make it perfect for aquascapes, planted tanks and peaceful community setups. In this guide you will learn how to choose, keep and breed this unique species, and how MB Store can support you with high‑quality aquariums and aquarium equipment tailored to their needs.

Origin and natural habitat of the Galaxy Rasbora

Celestichthys margaritatus was discovered relatively recently, in 2006, in small ponds and wetlands in Myanmar. These biotopes are shallow, overgrown with grasses and aquatic plants, and often exposed to strong sunlight. The water is usually clear, slightly alkaline or neutral, and rich in microfauna.

Despite the name “rasbora”, genetically the species is closer to danios, which is why the trade also uses the name Celestial Pearl Danio. In nature, groups of these fish stay close to dense vegetation where they can hide from predators and search for microorganisms and small invertebrates. For aquarists this means that a well‑planted tank with many hiding spots will best mimic their natural environment and help them feel safe.

In the early years after discovery there was concern about overfishing in the wild, because the species became extremely popular. Today the majority of individuals in the trade come from captive breeding, which reduces pressure on wild populations and makes the fish more robust and adapted to aquarium life.

Appearance and behavior

The Galaxy Rasbora is small but visually striking. Adults usually reach around 2–2.5 cm in length, making them ideal residents for nano aquariums. The body is dark blue to navy with cream or golden spots resembling a starry sky. This “galaxy” pattern is what gave the fish its common name. The fins are often bright orange or red with dark edges, especially in males.

Sexual dimorphism is visible but subtle. Males tend to be more intensely colored, with stronger contrast on the body and fins. Females are slightly rounder, especially when full of eggs, and their colors are more subdued. In a group, males often show off to each other, spreading their fins wide and performing short chases to demonstrate condition. These displays are not aggressive in a harmful way; they are part of normal social behavior.

Galaxy Rasboras are peaceful, shy and sensitive to stress. They are true schooling fish and should be kept in a group of at least 8–10 individuals. In a larger group, they feel safer, display more natural behavior and show better colors. Single fish or pairs often hide constantly and become pale.

Their behavior is perfect for densely planted aquariums and aquascapes. They prefer middle and lower water layers, frequently swimming between stems of plants and over moss carpets. When kept in good conditions, they can live 3–5 years, which is a respectable lifespan for such a small species.

Aquarium requirements for Celestichthys margaritatus

Thanks to their small size, Galaxy Rasboras are often associated with nano aquariums. A group of 10 fish can live in a tank of around 30 liters, but providing more space is always beneficial. A longer aquarium is preferred over a tall one, as it gives them more horizontal swimming space and allows for more complex hardscape and planting.

MB Store offers a wide range of aquariums, from compact nano tanks to larger planted setups, so you can easily choose a format that fits both your fish and your interior. When selecting an aquarium, consider not only volume but also the possibility of installing a filter, heater and lighting tailored to plants.

Water parameters for Galaxy Rasbora are relatively flexible, but stability is crucial:

• Temperature: 22–26 °C
• pH: 6.5–7.5 (slightly acidic to neutral)
• Hardness: soft to medium hard water

They do not like strong currents. A gentle flow allows them to swim calmly and feed without much effort. Filtration should be efficient, but the output must be adjusted or dispersed, for example using a spray bar. A good quality internal or external filter from MB Store will help maintain crystal‑clear, biologically stable water while keeping the current moderate.

Regular water changes are vital. Because these are sensitive fish, sudden spikes of ammonia or nitrite can be fatal. Weekly changes of 25–40% with well‑conditioned water of similar temperature and parameters keep stress to a minimum and support longevity.

Aquascaping, substrate and plants

The natural, slightly overgrown environment of the Galaxy Rasbora makes them a perfect choice for lush planted aquariums. They feel safest in a tank with many plants, roots and stones that break lines of sight and offer hiding places. An open, bare setup usually causes them to hide and show less color.

Dark substrate, such as black soil or dark sand, makes the fish’s colors appear more intense and gives the aquarium a more natural look. Active plant substrates also help stabilize water chemistry and provide nutrients for plants. MB Store provides different types of substrate and soil, so both beginners and advanced aquascapers can find something suitable for their projects.

Recommended plants for a Galaxy Rasbora aquarium include:

• Fine‑leaved stems like Rotala, Myriophyllum, Limnophila
• Foreground carpets such as Hemianthus callitrichoides, Glossostigma or Eleocharis
• Mosses (Taxiphyllum, Vesicularia) on roots and stones
• Floating plants that diffuse the light and give a sense of security

Wood and rocks can be arranged to create caves, arches and shaded areas. This structure helps the fish set up small territories, especially during breeding, and prevents weaker individuals from being constantly exposed. Strong lighting brings out plant growth and fish colors, but it is important to balance it with CO₂ and nutrients to avoid algae. MB Store offers lighting systems designed for planted aquariums, which make achieving this balance much easier.

Water quality, filtration and essential equipment

Although Galaxy Rasboras are small and do not produce as much waste as larger fish, in nano aquariums even small imbalances can cause problems. Efficient and stable biological filtration is essential. A filter with a sponge and biological media will provide a home for nitrifying bacteria that convert toxic ammonia into less harmful nitrate.

MB Store supplies a wide range of filters, heaters and other aquarium equipment suitable for tanks of any size. When choosing a filter, pay attention to its capacity, ability to regulate the flow and the volume of biological media. In many cases, an external canister filter with a spray bar is the best solution for planted community tanks with Galaxy Rasboras.

A heater is recommended even if your room temperature is relatively high. Fluctuations at night or during colder months can stress these delicate fish. A reliable heater with a thermostat keeps the temperature within the desired range. A digital thermometer allows constant control and quick reaction if something changes.

Regular maintenance should include:

• Weekly water changes and substrate vacuuming (gently, to avoid uprooting plants)
• Cleaning filter sponges in tank water to preserve beneficial bacteria
• Monitoring water parameters (NH₃/NH₄, NO₂, NO₃, pH, GH, KH) with test kits
• Trimming plants and removing decaying leaves

Stable conditions and good water quality are the best protection against disease. Many problems that appear as infections or parasites are in fact the result of stress and weakened immune systems due to poor maintenance.

Feeding Galaxy Rasboras

In nature, Celestichthys margaritatus feed on small invertebrates, insect larvae and planktonic organisms. In the aquarium they accept high‑quality dry foods, but the diet should be varied and tailored to their small mouths. Choose fine granules, micro‑pellets or crushed flakes that sink slowly and are easy to bite.

MB Store offers fish food suitable for nano species, including specialized micro pellets rich in protein and vitamins. A diverse diet can include:

• High‑quality dry micro‑granules and flakes
• Frozen foods (cyclops, daphnia, finely chopped bloodworms)
• Live foods (microworms, Artemia nauplii, small daphnia) if available

Feed them 1–2 times a day with portions they can consume in a few minutes. Overfeeding is dangerous in small aquariums because uneaten food quickly decomposes and worsens water quality. Observe how your Galaxy Rasboras feed: healthy fish actively search for food, swim confidently and show good coloration.

Occasional fasting days (once a week) help maintain digestive health and reduce the risk of obesity, which can be a problem in fish that are fed too often or too much. Combining dry and frozen or live foods better reflects their natural diet and enhances color and vitality.

Tank mates and community setups

One of the advantages of Galaxy Rasboras is their compatibility with many other small, peaceful species. They are ideal residents for planted community aquariums dedicated to nano fish and shrimp. Because they are shy and delicate, tank mates should be carefully selected.

Suitable companions include:

• Other small rasboras (Boraras brigittae, Boraras urophthalmoides)
• Small danios and peaceful tetras of similar size
• Pygmy Corydoras and other miniature bottom dwellers
• Dwarf shrimp (Neocaridina, Caridina) in well‑planted tanks
• Small snails such as Neritina or Clithon

Avoid large, predatory or very active fish such as big barbs, cichlids or large gouramis. They may outcompete Galaxy Rasboras for food, harass them or treat them as prey. Even if predation does not occur, constant stress will affect health and color.

In an ideal setup, the Galaxy Rasbora group forms the main midwater school, with shrimp or small bottom fish taking care of algae and leftovers, and perhaps a contrasting species in the upper layer. Such a composition creates a dynamic yet harmonious display where each level of the aquarium is active and visually interesting.

Breeding Celestichthys margaritatus in the aquarium

Breeding Galaxy Rasboras is possible and quite rewarding, especially for aquarists who enjoy observing natural behavior and raising fry. These fish are egg scatterers and do not show parental care. With adequate preparation, many hobbyists manage to obtain healthy offspring in home aquariums.

To encourage spawning, begin by conditioning a group of 8–10 fish with rich foods, especially frozen and live varieties. Good nutrition improves the condition of females and intensifies the colors of males. Provide dense plantings, especially fine‑leaved plants and mosses, where the fish can deposit eggs.

There are two main breeding approaches:

• Spontaneous breeding in the main tank: In heavily planted aquariums with many hiding spots, some fry may survive even without special measures. Adults will eat part of the eggs and larvae, but with dense moss carpets a few young fish can reach a safe size.
• Controlled breeding in a separate tank: A small 20–30 liter tank with a sponge filter, moss and similar water parameters is prepared. A group or pair of well‑conditioned adults is introduced for a few days. After spawning, adults are removed to protect eggs and fry.

Eggs hatch in about 2–3 days, depending on temperature. Initially, the larvae feed from their yolk sac and then start to swim freely. At this stage they require microscopic foods: infusoria, liquid fry food or very fine powdered fry food. After several days, Artemia nauplii and microworms become suitable.

Fry are extremely small and sensitive to water quality, so gentle filtration and frequent small water changes are essential. A sponge filter driven by an air pump from MB Store will provide safe, oxygen‑rich water without the risk of sucking in the young. As the fry grow, they can gradually be introduced to crushed dry foods and moved to larger tanks.

Watching the development from tiny translucent fry to fully colored miniature “galaxies” is one of the most satisfying experiences for dedicated aquarists and demonstrates how well‑maintained, stable conditions and proper equipment lead to success.

Why Galaxy Rasboras are perfect for modern aquariums

Celestichthys margaritatus combines many traits that make it almost ideal for planted and design‑oriented aquariums. The small size fits perfectly with contemporary living spaces where compact tanks are often preferred. The intense pattern stands out against green plants and dark substrates, turning every movement into a small, colorful flash.

From a fishkeeping perspective, Galaxy Rasboras reward careful care with vibrant colors, natural schooling behavior and a surprisingly long lifespan for their size. They are not the best choice for completely inexperienced aquarists starting without guidance, but with basic understanding of the nitrogen cycle and access to reliable equipment from MB Store, they are absolutely manageable.

MB Store supports aquarists at every step: from choosing the right aquarium size and filter, through selecting lighting, substrate and water conditioners, to providing specialized foods and accessories for breeding. With a well‑planned setup and thoughtful stocking, a group of Galaxy Rasboras can become the centerpiece of a tranquil, nature‑inspired underwater landscape in your home or office.

Whether you are building your first planted nano tank or refining an advanced aquascape, this species offers beauty, interesting behavior and the opportunity to observe subtle social interactions on a miniature scale. With patience, regular maintenance and appropriate technology, your aquarium can become a living “galaxy” full of movement and color.

FAQ

How many Galaxy Rasboras should I keep together?
Galaxy Rasboras are schooling fish and feel best in larger groups. A minimum of 8–10 individuals is recommended, but if your aquarium is spacious enough, a group of 15 or more will show even more natural behavior. In a larger school, the fish are less shy, display brighter colors and explore the tank more confidently.

Can Galaxy Rasboras live in a 20‑liter nano tank?
A 20‑liter aquarium is the absolute minimum and only suitable for a small group of fish under the care of an experienced aquarist. Better results are achieved from 30 liters upwards, where water parameters are more stable. Regardless of volume, the tank should be well planted, filtered and maintained with regular water changes.

Are Galaxy Rasboras compatible with shrimp?
Galaxy Rasboras generally coexist peacefully with dwarf shrimp like Neocaridina. Adult shrimp are usually safe, but very small shrimplets may occasionally be eaten if they wander into open areas. Dense plants and moss help young shrimp hide. A well‑structured aquascape allows both species to thrive together.

What is the best temperature for Celestichthys margaritatus?
The optimal temperature range is 22–26 °C. Slightly lower temperatures around 23–24 °C may increase lifespan but slow growth, while warmer water speeds up metabolism. Avoid sudden fluctuations of more than 1–2 °C per day. A reliable heater and thermometer help keep the temperature stable and protect the fish from stress.

How long do Galaxy Rasboras live in captivity?
With good care, Galaxy Rasboras typically live 3–5 years. Key factors influencing lifespan are water quality, appropriate diet, the absence of aggressive tank mates and stable environmental conditions. Regular maintenance, good filtration and a varied, high‑quality diet significantly increase their chances of reaching the upper end of that range.