Green Neon (Kubotai) Rasbora Care Guide

The kubotai or green neon rasbora is a tiny (~2 cm) hill-stream schooler that glows electric green over dark substrate. The one care point most buyers miss: this is not a still-water blackwater nano but a fish from flowing, well-oxygenated headwaters, so it actually wants gentle current and good oxygen. It is genuinely peaceful, but at 2 cm it is also bite-size prey, so it belongs in a nano-specific tank with nano-scale tankmates, never as a splash of green added to a tank with bigger fish.

Green Neon (Kubotai) Rasbora at a glance

The sourced figures the welfare engine uses to judge Green Neon (Kubotai) Rasbora — the parseable key facts.

Where it comes from

Microdevario kubotai comes from clear hill streams in north-western peninsular Thailand and the Ataran (Salween) drainage of southern Myanmar — calm to moderately-flowing, well-oxygenated headwaters and minor tributaries over sand and gravel, with leaf litter, driftwood and vegetation. That origin sets it apart from blackwater nanos in three ways: the flowing, oxygen-rich water means it likes some current and is an active swimmer, not a still-tank fish; the clear hill streams mean it sits at soft-to-neutral water rather than demanding the acidic blackwater a green neon tetra wants; and its cool-to-warm streams mean it tolerates the cooler end of the tropical range. Plant densely over dark substrate to mimic the shaded stream bed and the green comes alive.

Did you know?

• It is named after a person — the epithet kubotai honours collector Katsuma Kubota, thanked for fieldwork help and 'the gift of numerous specimens'.
• It changed its scientific name twice: described in 1999 as Microrasbora kubotai, then moved in 2009 to the new genus Microdevario when DNA showed the old Microrasbora group wasn't a natural unit — which is why shops sell the same fish under two names.
• Green in the tank, yellow in the wild. FishBase records it as translucent yellow in the field but greenish-yellow with a glowing golden stripe in aquaria, so the neon-green look is largely a product of aquarium lighting and dark substrate.
• 'Green neon' but not a tetra — it shares a marketing name with the South American green neon tetra yet is an Asian cyprinid from a different family and continent, a genuinely useful myth-buster for buyers.
• A schooling fish that really schools: in its Thai and Myanmar hill streams it lives in shoals of twenty to fifty, which is why it looks and behaves best in big aquarium groups. The IUCN lists it as Least Concern.

Tank size — and why

A 10 US gallon tank is a workable minimum for a starter school, but the better real-world floor is a 15 gallon, 60 × 30 cm footprint — that is the size Seriously Fish and FishBase specify, and it gives both the swimming length an active, tight-schooling nano wants and the water-volume stability a sensitive small fish needs. Bioload is not the driver here: a 2 cm, low-waste fish makes almost no mess, so the constraint is room for a proper ten-plus school and the steadiness of a larger volume. Prioritise length over height — these are active horizontal swimmers — and keep a lid on, since small fish can be lost over an open rim.

As a guide, a 20-gallon tank comfortably suits about 9–13 Green Neon (Kubotai) Rasbora as a single-species display, leaving room for tankmates.

See it to scale

Adult Green Neon (Kubotai) Rasbora reach only about 2 cm (0.8 in) long — close to the size they are sold at, so what you see is roughly what you get. The catch is the group: a proper shoal still needs about a 10-gallon tank, around 51 cm long.

Adult size is sourced; tank length is approximate for a standard 10-gallon aquarium.

Water parameters in practice

Aim for about 22-26 °C (it tolerates 20-28 °C) and a soft-to-neutral pH around 6.5, comfortably within roughly 6.0-7.0 in soft to moderately soft water. Two things matter beyond the table. First, the cool tolerance is real — its hill-stream origin means it copes down to around 20 °C and does not need to be kept hot, which widens its compatible range. Second, and unlike the green neon tetra it is often confused with, it does not want extreme acidic blackwater; it is happy around neutral, a clear-stream fish not a blackwater specialist. It is described as a timid fish that stresses easily and may not be the hardiest, most vulnerable to poor water quality, high nitrate, low oxygen and sudden swings, so add it only to a mature, cycled, stable, well-oxygenated tank and value stability over an exact pH.

Diet & feeding

A micro-omnivore that takes small invertebrates and zooplankton in the stream. Because of the tiny mouth, food must be small — a quality micro or crushed flake, nano pellet or fine granule as the base. Supplement with small live and frozen foods such as daphnia, baby brine shrimp, cyclops, microworm and finely chopped bloodworm to boost colour and breeding condition; it does best with these alongside dried food. Feed small amounts once or twice a day, or several tiny feeds, since the small stomach means sparing feeding protects water quality and small frequent feeds keep the colour vivid. As active mid-water feeders they can be out-competed by faster or larger tankmates, which is another reason to keep them only with nano fish.

Gear & setup

A planted nano tank with dark substrate to intensify the green, fine-leaved plants, driftwood and some leaf litter for security and biotope feel. A heater holds a stable mid-20s, though it tolerates the cooler end. The defining kit requirement is flow and oxygen: this is a flowing-headwater fish, so provide gentle-to-moderate current and good surface agitation, and avoid stagnant, low-oxygen setups — a still tank is a real stressor here, the opposite of a blackwater Boraras. A lid is sensible for an active small fish.

Temperament & behaviour

Peaceful and tight-schooling, with no territoriality, no fin-nipping and no same-species aggression — Seriously Fish calls it 'very peaceful but best maintained alone or with comparably-sized species'. The only threat runs the other way: it is prey. The behaviour the buyer wants appears in numbers and security — a big group in a planted tank with some flow forms a confident, bold, electric-green school, while a few fish or oversized tankmates leave it pale, hidden and chronically stressed. Rapid gilling is worth watching, as for this species it often signals an oxygen or flow shortfall rather than disease.

Group & social needs

Keep a large group. Eight is the common minimum (Seriously Fish and FishBase note 8-10), but the fish schools best at ten-plus, ideally ten to twenty, and in the wild lives in shoals of twenty to fifty. Twelve to fifteen looks best in a nano tank. Treat eight as the bare floor and never fewer: in small groups it is skittish, washed-out, hiding and chronically stressed, and stress kills this sensitive nano. Bigger groups give confidence, tighter schooling, better colour and dilute any individual's exposure.

Compatible tank mates (preview)

A short, engine-cleared shortlist — the species TankStocking's welfare engine clears with Green Neon (Kubotai) Rasbora and that suit its size and temperament best. Tap any to load the pairing in the planner.

• Assassin Snail — Uses the bottom zone, peaceful temperament, similar adult size.
• Black Neon Tetra — Peaceful temperament, similar adult size.
• Black Phantom Tetra — Peaceful temperament, similar adult size.

A note on the shrimp and snails here: Green Neon (Kubotai) Rasbora is peaceful and generally invertebrate-safe — but almost any fish will take very small shrimplets given the chance, so give shrimp dense cover (moss, leaf litter) if you want a colony to grow, rather than expecting every baby to survive.

This engine-cleared shortlist is Green Neon (Kubotai) Rasbora's tankmate surface for now — a dedicated tank-mates guide can follow for high-demand species.

Breeding & sexing

Sexing is subtle — mature females are deeper-bodied and noticeably larger, while males are more compact and intensely coloured; they are hard to sex when young or out of condition. It is an egg-scatterer that spawns continuously among plants with no parental care, the adults eating the eggs. Set up a separate, densely planted soft-water tank with fine-leaved plants, spawning mops or moss and gentle flow, condition the fish on small live foods, and remove the adults after spawning to protect the eggs. Incubation is around 72 hours per Seriously Fish, with fry free-swimming a few days later (some hobby pages quote shorter hatches, so treat ~72 h as the primary figure). Difficulty is moderate: they spawn readily in a mature planted tank, but the bottleneck is raising the tiny fry, which need infusoria or microscopic first foods before microworm and baby brine shrimp.

Lifespan

Roughly three to five years in a well-kept nano tank, with one care source citing up to seven; treat three to five as the realistic expectation and five-plus as achievable with stable water and a calm tank. What shortens it is chronically poor water quality and high nitrate, low oxygen and stagnant water (against its flowing-stream nature), sudden parameter swings, chronic stress from too small a group or oversized tankmates, and shipping or import damage on already-stressed wild-caught stock.

Common mistakes

• Treating it as a general community fish. At 2 cm it is prey — housing it with angelfish, gouramis, larger barbs or any bigger fish ends in losses. Compatibility is set by tankmate mouth size, not by its gentle temperament, so keep nano-safe tankmates only.
• Too small a group. One to six fish go skittish, faded, hidden and short-lived — buy ten or more, with eight the absolute minimum.
• Stagnant, under-oxygenated water. This is a flowing-headwater fish, so a still, low-oxygen tank stresses and shortens it — provide gentle-to-moderate flow and good surface movement.
• Adding it to an immature or unstable tank. A sensitive nano that reacts badly to nitrate spikes and parameter swings needs a mature, cycled, stable tank.
• A bright, bare tank that washes out the colour. Dark substrate and dense planting are what show the green.
• Confusing it with the green neon tetra. The rasbora is an Asian cyprinid (green-gold, soft-to-neutral water); the green neon tetra is a South American characin (blue-green with red, blackwater). They share a marketing name only.

Signs of trouble

• Colour fading to washed-out or translucent and a fish dropping out of the school — usually too small a group, a bright tank, or stress.
• Rapid gilling — for this species often an oxygen or flow problem rather than disease; check surface movement and current.
• Clamped fins, hiding and skittishness — general stress, frequently from an under-sized group, oversized tankmates, or an unstable tank.
• Flicking, white spots, velvet dusting or fungal patches — standard nano ailments, usually triggered by chilling, stress or poor water.
• Thin, lethargic fish in the weeks after purchase — import and shipping stress on wild-caught stock; quarantine and acclimate slowly.

Is this fish right for you?

Don't buy kubotai rasboras for an existing tank holding fish bigger than about 3-4 cm; if you can't keep a group of ten; if you have a stagnant or low-oxygen setup; if your tank is brand-new and uncycled; or if you actually wanted the green neon tetra, a separate South American blackwater characin. Much trade stock is wild-caught and import-stressed, so prioritise healthy, active fish from an established tank and quarantine them. There are no dyed or balloon morphs to worry about for this species.

Bringing one home

Add kubotai rasboras only to a mature, cycled, stable, well-oxygenated tank with gentle flow, and acclimate slowly — much stock is wild-caught and import-stressed, so float to match temperature, add tank water gradually over fifteen to twenty minutes, then net the fish across and leave the transport water behind. Quarantine new arrivals and buy active, well-coloured fish from an established tank rather than thin, faded ones.

Common questions

What is the difference between a green neon rasbora and a green neon tetra?

They share a marketing name but are unrelated. The green neon rasbora (Microdevario kubotai) is an Asian cyprinid with a green-gold stripe and no red, happy in soft-to-neutral water. The green neon tetra (Paracheirodon simulans) is a South American characin with a blue-green stripe plus some red, and it wants acidic blackwater. Different family, continent and water needs.

Do kubotai rasboras need water flow?

Yes — this is its defining and most-missed need. It comes from flowing, well-oxygenated hill streams, so it wants gentle-to-moderate current and good surface movement, not the still water of a blackwater nano tank. A stagnant, low-oxygen setup stresses and shortens it.

How many kubotai rasboras should I keep?

Eight is the bare minimum; ten or more (ideally ten to twenty) is the real target, and twelve to fifteen looks best in a nano tank. They live in wild shoals of twenty to fifty, and in small groups they are skittish, faded and chronically stressed.

Are kubotai rasboras good community fish?

Only in a nano community. They are perfectly peaceful and harm nothing, but at ~2 cm they are bite-size prey — anything large enough to eat them (angelfish, larger gouramis and barbs, cichlids) will. Keep them only with other nano-scale fish; compatibility is set by tankmate mouth size, not by their temperament.

Why is my kubotai rasbora not green / looking pale?

Usually too small a group, a bright or bare tank, or stress. A big secure shoal over dark substrate in a planted, well-oxygenated tank brings the electric green out; the colour is light-dependent and fades in poor conditions.

Sources & confidence

Sources & confidence (9 species)

These back the Green Neon (Kubotai) Rasbora figures and the previewed tank mates above. Each figure is read from the TankStocking species database (v2026.06); below is the care reference behind it and how confident we are in that data. Confidence reflects the source quality, not whether any pairing is safe. Full source list and the welfare model are on the methodology page.

• Green Neon (Kubotai) Rasbora Microdevario kubotai — Seriously Fish (seriouslyfish.com/species/microdevario-kubotai) high confidence
• Assassin Snail Clea helena (Anentome helena) — The Shrimp Farm (theshrimpfarm.com/posts/assassin-snail-care) high confidence
• Black Neon Tetra Hyphessobrycon herbertaxelrodi — Seriously Fish / Aqua-Fish (Hyphessobrycon herbertaxelrodi) high confidence
• Black Phantom Tetra Hyphessobrycon megalopterus — Seriously Fish (Hyphessobrycon megalopterus) high confidence
• Cardinal Tetra Paracheirodon axelrodi — Seriously Fish (seriouslyfish.com/species/paracheirodon-axelrodi) high confidence
• Celestial Pearl Danio Celestichthys margaritatus — Seriously Fish (seriouslyfish.com/species/celestichthys-margaritatus) high confidence
• Cherry Shrimp Neocaridina davidi — Aquarium Co-Op cherry shrimp care; The Shrimp Farm high confidence
• Chili Rasbora Boraras brigittae — Seriously Fish (seriouslyfish.com/species/boraras-brigittae) high confidence
• Clown Killifish Epiplatys annulatus — Seriously Fish (Epiplatys annulatus); Aquarium Co-Op high confidence

Care-guide sources (7)

This guide synthesises the references below; where they disagree, the range and the disagreement are noted in the text above. The figures in the key-facts box are read from the TankStocking species database (v2026.06). Full welfare model on the methodology page.

• FishBase — Microdevario kubotai — authority (Kottelat & Witte, 1999), family Danionidae, max 1.9 cm SL, freshwater/benthopelagic tropical, Thailand/Myanmar range, trophic level 3.0, IUCN Least Concern (assessed 19 Feb 2011), resilience high / vulnerability low, field-vs-aquarium colour ('translucent yellow … glowing golden lateral stripe')
• Seriously Fish — Microdevario kubotai (Microrasbora kubotai) — authority and genus history, synonym Microrasbora kubotai, family Cyprinidae, biotope ('calm to moderately-flowing … well-oxygenated headwaters'), 15-20 mm SL, temp 20-27 °C, pH 6.0-7.0, GH 18-179 ppm, 60×30 cm / 54 L tank, group 8-10 (wild 20-50), diet, 'very peaceful' temperament quote, named nano tankmates, sexing, scatter-spawning with ~72 h incubation
• GBIF + Wikispecies (taxonomy & etymology) — confirms authority (Kottelat & Witte, 1999) and the 1999 description, the Microrasbora→Microdevario (Fang et al. 2009) reclassification, and the etymology honouring Katsuma Kubota
• Steenfott Aquatics — Neon Green Rasbora care guide — size 2-2.5 cm, temp 72-80 °F, pH 6.0-7.0, 10 gal (15-20 recommended), group 8-10, micro-predator diet, nano tankmate lists (ember tetra, small rasboras, cories, dwarf shrimp, Pseudomugil), egg-scatterer
• Fish Laboratory — Neon Green Rasbora: Care & Lifespan — lifespan 3-7 yr, size ~2 cm, temp 20-27 °C, pH 6.0-7.0, GH 18-179 ppm, 15 gal for ~8 fish, group 8 (wild 20-50), sexing, 'small timid fish that can easily get stressed', diseases (ich/velvet/fungal), import/shipping stress
• Horizon Aquatics — Green Kubotai Rasbora care guide — size 2-2.5 cm, lifespan 4-5 yr, temp 22-28 °C, pH 6.0-7.5, 'peaceful, energetic, tight-schooling', school 10-20+, gentle-to-moderate flow, low-oxygen/nitrate sensitivity, good/avoid tankmate lists, breeding notes
• Keeping Tropical Fish (UK) — Keeping Neon Green Rasbora — temp 20-27 °C, pH 6.0-7.0, 15 gal / 54 L, group 'at least 8, more is better', gentle flow, varied diet, peaceful, 'avoid aggressive or large tank mates', egg-scatterer, 'may not be the hardiest fish'

More on Green Neon (Kubotai) Rasbora

Related guides on TankStocking — each scored by the same welfare engine as the planner.

This care guide is a sourced planning reference, not veterinary advice — individual fish, filtration and maintenance all matter. Cycle the tank, test your water, and observe your fish. How TankStocking works →