In the fascinating universe of micro fish, few species shine with the intensity and charm of the Kubotai Rasbora (Microdevario kubotai). Also known as Neon Green Rasbora or Emerald Rasbora, this tiny gem from Southeast Asia is an explosion of electric green color that captivates any enthusiast. Its small size, peaceful temperament, and vibrant coloration have made it one of the favorite choices for nano aquariums and planted tanks, where a school of these tiny wonders looks like a swarm of green fireflies dancing among the vegetation.
Although its history in aquaristics is not as long as that of other fish, its popularity has continued to grow. In this complete guide, we will delve into the world of the Kubotai Rasbora. You will discover everything you need to keep it healthy and at its brightest: from the ideal aquarium size and perfect tank mates, to the secrets of its feeding and the challenging task of breeding. Plus, we’ll give you an expert tip for setting up an aquarium that highlights its color spectacularly.
The Streams of Thailand: Its Natural Habitat
The Kubotai Rasbora is native to the streams and small rivers of the Mae Klong and Ataran river basins, on the border between Thailand and Myanmar. It prefers calm, clear, shallow waters with abundant submerged and riparian vegetation. These environments typically have sandy or fine gravel bottoms, covered with leaf litter and small branches, resulting in soft water with a slightly acidic or neutral pH. It is in this serene environment that they form schools, seeking safety and food among the plants and roots.
A Flash of Emerald Color: Morphology
The most striking feature of the Kubotai Rasbora is, without a doubt, its color. Its body displays a spectacular neon green or emerald hue that glows intensely under aquarium lighting. This color is not solid, but has a metallic sheen that reflects light, creating a dazzling visual effect, especially when they are calm and well-adapted to their environment.
They are truly tiny fish. Females, slightly larger and rounder, barely reach 2 cm (0.8 inches), while males are a bit smaller and more slender. Their small size is one of their greatest advantages, but also a factor to consider when planning their aquarium and feeding.
The Miniature Home: Minimum Aquarium Size and Parameters
Aquarium Size
Thanks to their small size, they are perfect candidates for nano aquariums. A small school (6-8 specimens) can be kept in an aquarium of 20 to 25 liters (5-7 gallons) minimum. However, to appreciate their schooling behavior more naturally and give them more space, a 40-50 liter (10-13 gallon) aquarium is ideal, allowing for a group of 15 or more individuals.
Water Parameters: The Key to Soft Water
For Kubotai Rasboras to show their best color and stay healthy, we must replicate the conditions of their natural habitat:
- Temperature: Between 22°C and 26°C (72°F – 79°F).
- pH: Slightly acidic to neutral, ideally between 6.0 and 7.0.
- Hardness (GH): They prefer soft water. A GH below 10 dGH is ideal for their long-term well-being.
- Water Quality: They are sensitive to nitrogenous compounds. It is crucial to keep ammonia and nitrites at zero, and nitrates as low as possible with good maintenance.
A Peaceful Community: Compatibility with Other Fish
Their temperament is extremely peaceful, but their tiny size makes them potential prey for many fish. The choice of tank mates must be very careful.
- Ideal Tank Mates: They are perfect for a nano community aquarium with other micro fish such as Galaxy Rasboras (Danio margaritatus), Chili Rasboras (Boraras brigittae), small Tetras like Ember Tetras, or Pygmy Corydoras.
- Invertebrates: They are excellent companions for shrimp (Neocaridina like Red Cherry and Caridina) and snails. They will not prey on adult shrimp and will rarely bother fry.
- To Avoid: Any fish large enough to fit them in their mouth, including Bettas, most larger Tetras, Gouramis, and, of course, Cichlids.
Small Mouths, Small Food: Feeding
They are omnivorous and generally not picky, but the limiting factor is the tiny size of their mouths.
- Dry Food: The basis of their diet should be high-quality granules or flakes specifically formulated for micro fish. The food must be almost powder-like for them to ingest it.
- Frozen Food: They will readily accept very small frozen foods, such as cyclops, daphnia, or brine shrimp nauplii. Large bloodworms are impossible for them to eat.
- Feeding: They usually eat in the upper and middle sections of the aquarium. It is best to give them small amounts several times a day to ensure all food is consumed before it falls to the bottom.
The Breeding Challenge: Reproduction and Lifespan
With a lifespan of about 4-5 years, breeding the Kubotai Rasbora in a home aquarium is a considerable challenge.
- Sexual Dimorphism: Females are slightly larger and, when ready to spawn, have a more rounded belly. Males are more slender and often display a more intense color.
- Breeding Process: They are free-spawning oviparous fish. The male performs a courtship display, and the pair scatters eggs, often among fine-leaved plants like Java moss. They show no parental care and will eat their own eggs and fry.
- Raising Fry: To succeed, a specific breeding tank is needed with a bottom grid or filled with moss to protect the eggs. The fry are incredibly tiny and require microscopic food like infusoria or rotifers during the early stages, before they can transition to brine shrimp nauplii. Raising them in a community aquarium is practically impossible.
Expert Tip: An Aquascape to Maximize Their Shine
While the Kubotai Rasbora looks spectacular in a densely planted aquarium (aquascaping), there is a particular aquascaping style that makes its green color stand out uniquely.
The “Light Blackwater” Setup:
- Substrate: Use dark or neutral-colored sand.
- Hardscape (Rocks and Wood): Create a complex structure with many fine roots and dark driftwood that generate shaded areas and small caves.
- Leaf Litter: Cover the bottom of the aquarium with a layer of Indian almond leaves (Catappa) or oak leaves. This not only recreates their biotope but the dark color of the bottom creates an incredible contrast.
- No Plants (or Very Few): While it sounds counterintuitive, by not having the green of plants visually competing, the metallic, shimmering green of the Kubotai becomes the absolute star. The contrast between dark wood, brown leaves, and the emerald flash of the fish is simply stunning.
This setup provides them with the security of the refuges and shadows they love, and allows you to enjoy their color in its maximum expression.
Conclusion: A Small Treasure Full of Life
The Kubotai Rasbora is much more than a small fish; it is a living jewel that brings dynamism, color, and elegance to small aquariums. Its peaceful nature and compatibility with invertebrates make it an ideal choice for lovers of nano ecosystems. Although its reproduction is a challenge, its daily care is straightforward as long as its needs for space and water quality are met. If you are looking for a fish that will transform your small aquarium into a vibrant spectacle of light and color, look no further: a school of Kubotai Rasboras is the perfect choice.
FAQs
How many Kubotai Rasboras should I keep at a minimum?
They are schooling fish and feel insecure if kept alone. You should keep a group of at least 6 to 8 specimens as an absolute minimum, although a group of 10 or more is much better for their well-being.
Are they difficult fish for beginners?
They are not particularly difficult if you have the right aquarium. Their main requirement is a mature tank with stable water parameters (especially pH and hardness) and appropriate tank mates. They are an excellent choice for a beginner starting with a well-planned nano aquarium.
My Kubotai Rasboras’ color is pale, what could be wrong?
Paleness in their color is usually a sign of stress. Common causes include: a new, uncycled aquarium, incorrect water parameters (pH or GH too high), a school that is too small, or the presence of larger fish that intimidate them.
Can they live with a Betta fish?
It is not recommended. While some Bettas are peaceful, many may view Kubotai Rasboras as prey due to their small size and quick movement. It’s a risk best avoided.
Do they need a lot of current in the aquarium?
No, quite the opposite. They come from very calm waters. The filter output should be gentle to avoid creating a strong current that would stress them and make swimming difficult. Using a sponge filter is an excellent option for their aquariums.