Neon Green Rasbora (Microdevario kubotai)

Neon Green Rasbora care at a glance

These figures are planning ranges, not permission to make abrupt changes. A fish already settled in stable water should not be moved rapidly from one end of a range to the other. Test the source and destination water, acclimate gradually and favour consistency.

Identity, accepted name and useful search names

The accepted name used on this listing is Microdevario kubotai. The species was originally described as Microrasbora kubotai, so the former combination still appears in older books, retailer catalogues and aquarium discussions. “Kubotai Rasbora”, “Green Kubotai Rasbora”, “Neon Green Rasbora” and “Green Neon Rasbora” are trade or common names for the same fish when they are paired with the scientific name Microdevario kubotai.

Using the scientific name matters because common names can overlap. “Green neon” is also used for a small South American tetra, and “emerald rasbora” may refer to other Asian fishes. The scientific name is the most reliable identity check when comparing care information, photographs or livestock. Current references place this species in the family Danionidae and subfamily Danioninae. Older sources may use a broader historical Cyprinidae placement; that difference reflects changes in classification rather than a different fish.

The name does not describe a fluorescent dye, injected colour or formal colour morph. It refers to the naturally reflective green-yellow appearance seen under aquarium lighting. A settled fish can look greener, more golden or more translucent according to the angle of light, background, stress level and individual condition. A pale new arrival is not automatically a different species, and an intensely edited photograph should not be treated as the only acceptable colour.

What an accurately identified fish should look like

Microdevario kubotai is a very small, slender, fusiform fish with a relatively large eye, a tiny terminal mouth and a clearly forked tail. FishBase describes wild fish as translucent yellow and aquarium-kept fish as greenish yellow, with a glowing golden lateral stripe and hyaline, or glass-like, fins. The body is lightly built rather than deep and chunky. The dorsal and anal fins should not turn the fish into a tall-bodied tetra shape, and the species does not carry the heavy red and black markings associated with many other rasboras.

Look at the whole combination of traits rather than colour alone: narrow body, clear fins, bright lateral sheen, large eye and small mouth. Lighting can make the stripe appear emerald, chartreuse or golden. Dark wood and substrate tend to increase visible contrast; a pale retail tank can make the same fish look washed out. Females may appear fuller through the abdomen when mature, while males are often slimmer, but sexing small or recently arrived fish from one photograph is unreliable.

Adult size, standard length and the dispatch-size options

FishBase records a maximum of 1.9 cm standard length for this species. Standard length is measured from the front of the snout to the base of the tail and does not include the caudal fin. Aquarium suppliers may quote total length, may round a batch measurement, or may use a dispatch-size band rather than a scientific maximum. This is why a shop option can state 1–2 cm or 2.5 cm without implying that two different species are being sold.

Treat the size selector as a description of the fish offered in that batch, not as a promise that every animal will measure to a single millimetre. Live fish grow at different rates and should not be expected to be identical. The selected option also should not change the long-term care plan: both sizes need the same mature aquarium, social group, feeding access and peaceful companions. Do not plan a smaller tank simply because the smaller dispatch option is selected.

Distribution and habitat lessons for the aquarium

The original species description places Microdevario kubotai on the western, Andaman Sea slope of Peninsular Thailand. Additional records are reported from the Ataran basin in Myanmar. Locality summaries therefore need to distinguish the type-description range from later reported records rather than treating every place named in the 1999 paper as a locality for the same species.

For aquarium care, the important habitat lesson is that this is an active small fish associated with clean, moving freshwater rather than a fish suited to stagnant, poorly oxygenated conditions. A planted aquarium can imitate the useful structure of a stream margin: fine leaves, shaded areas, roots or wood, broken sight lines and an open route through the middle. Moderate water movement can support oxygenation, but the fish must still be able to hold position, feed and rest without being pinned in one corner.

Natural-looking décor is valuable because it changes behaviour, not because a precise biotope is compulsory. Floating plants or tall stems can soften overhead light. Darker substrate and wood improve visual contrast. Dense cover near the back and sides gives the shoal somewhere to retreat, while a clear midwater lane allows its characteristic movement to be seen. Avoid filling every centimetre with hardscape; the group needs unobstructed swimming room as well as shelter.

Planning a mature 54-litre-or-larger aquarium

A 54-litre planning floor provides more useful stability and swimming room than a very small desktop aquarium. Shape matters alongside volume. A longer tank with a clear horizontal route is generally more useful for an active shoal than a narrow tall vessel holding the same litres. The final stocking level must consider the tank’s dimensions, filtration, maintenance routine and every other animal already present; a litre figure is not a complete stocking calculation.

Maturity and biological stability

“Mature” does not mean that a tank has simply stood for a fixed number of weeks. It means the filtration and husbandry routine can process waste reliably and the aquarium has demonstrated stable results. Before adding these fish, test that ammonia and nitrite are zero, understand the normal nitrate trend for the system, and confirm that temperature and pH do not swing sharply between maintenance visits. A test result is more useful than a calendar claim.

A newly cycled aquarium can technically process a measured waste load yet still be easy to destabilise through overfeeding, filter cleaning or a sudden increase in livestock. Tiny fish give little margin for neglect because a missed meal, intake accident or water-quality change can affect them quickly. If the tank has only recently completed its cycle, build confidence with repeated stable tests and a consistent routine before introducing the entire shoal.

Filtration, flow and oxygen

Choose filtration that maintains clear, oxygenated water without creating a dangerous intake or a single high-velocity jet. A sponge pre-filter can protect small fish and reduce the risk of food disappearing immediately into the filter. Direct the return along a pane or across the surface if the raw flow is too concentrated. Surface movement supports gas exchange, but violent splashing is not required.

Watch the fish rather than relying only on the filter’s advertised turnover. A comfortable group should be able to explore the tank, hold station and feed throughout the water column. If every fish is constantly forced behind one ornament, flow is not being used well. Conversely, persistent hovering at the surface, unusually rapid breathing or a sudden loss of activity needs prompt investigation of oxygen, temperature and water quality.

Plants, cover and open space

Use plants as functional structure. Fine-leaved stems and moss provide visual security and small feeding surfaces; floating growth diffuses harsh light; wood and taller plants create shaded zones. Keep an open central or front swimming lane so the group can move together. Secure décor, leave a safe gap around equipment and cover openings because small active fish can pass through spaces that look insignificant.

• Use a secure lid or cover and check cable, pipe and feeding gaps.
• Protect filter intakes and avoid exposed pump openings.
• Create planted shelter without removing all midwater swimming space.
• Keep the aquarium away from rapid temperature changes and uncontrolled direct sun.
• Test water regularly enough to recognise the tank’s normal pattern.
• Leave enough access to siphon debris and maintain the filter safely.

Water conditions: aim for stability within a sensible range

A practical care range is 20–27°C, pH 6.0–7.0 and approximately 1–10 dGH. The centre of the temperature range is often convenient for a planted community, but the correct target depends on the other livestock and the water in which the fish are already settled. Avoid rapid temperature or mineral changes made solely to reach an ideal-looking number.

Water with low alkalinity (KH) has limited buffering capacity, so pH may move more readily. That does not justify adding corrective chemicals without understanding the source water. Test tap or prepared water, tank water and replacement water. If remineralised reverse-osmosis water is used, measure and mix it consistently. If tap water already sits safely within the planning range, stability may be better than repeatedly adjusting it.

Routine partial water changes should remove dissolved waste while keeping temperature and chemistry close to the aquarium. Dechlorinate replacement water as required for the water supply and product instructions. Clean filter media in removed aquarium water or otherwise according to the filter manufacturer’s guidance, preserving biological function. Never replace all mature media at once unless an emergency and the consequences are understood.

Group size, shoaling behaviour and confidence

Plan a group of at least 10 Neon Green Rasboras. The purpose is not merely to make the tank look fuller. A larger same-species group gives these social fish more security, spreads normal chasing and produces more natural movement. A confident shoal can loosen across the tank when relaxed and draw together when startled; it does not need to swim as one rigid block all day.

Six fish may be a shop quantity-discount threshold, but it should not be presented as the welfare target for this species. Start with the long-term group plan and the aquarium’s capacity. Do not assume that one small rasbora species can replace the social needs of another. Related fish may occupy the same tank, but Microdevario kubotai still benefits from enough companions of its own kind.

Normal behaviour includes active midwater swimming, brief social following and rapid feeding movements. Persistent hiding, clamped fins, isolation, loss of balance or repeated failure to feed is not something to dismiss as shyness. Check group pressure, tank mates, flow, temperature, oxygen and water tests. Observe the shoal at quiet times as well as immediately after food is added.

Feeding tiny mouths without losing fish at the food queue

The main feeding challenge is particle size and access. Offer fine micro pellets, finely crushed quality flake and appropriately sized live or frozen foods such as Cyclops, daphnia and baby brine shrimp. Foods should be small enough to take easily and should remain available in the part of the water column where the fish feed. Large pellets that fall untouched to the bottom do not become useful simply because their ingredients are good.

Feed modest portions and observe the entire group. In a mixed tank, larger or faster fish can consume the obvious food before these tiny rasboras take enough. Distribute small food across more than one area, vary the direction of delivery, and watch quieter individuals. The correct portion is one the fish consume without leaving significant waste; a fixed pinch cannot suit every group, food density or tank.

A varied diet improves feeding opportunity and reduces dependence on one particle shape. Dry micro food is convenient for routine use, while small frozen or live foods can encourage a strong response. Thaw and portion frozen food appropriately rather than dropping an oversized block into a small aquarium. Do not assume the fish can live on incidental aquarium organisms or food left by tank mates.

Body-condition checks

View the fish from the side and above where possible. A healthy individual should not develop a persistently pinched abdomen or progressively lose body mass. Compare fish within the group: a single animal that always hangs back may be missing food even when the shoal as a whole looks active. Record changes rather than waiting for a severely thin fish.

• Choose genuinely small foods rather than crushing only the surface of a large pellet.
• Make sure food reaches more than one part of the shoal.
• Remove or siphon uneaten accumulations during maintenance.
• Adjust quantity after observation, not according to marketing instructions alone.
• Use feeding time to count fish and notice changes in appetite or position.

Tank mates: peaceful is not the same as universally compatible

Neon Green Rasboras are peaceful, but their small size makes them vulnerable to intimidation, accidental predation and food competition. The best companions are very small, calm fishes with overlapping water needs and feeding styles. Avoid choosing tank mates only because another listing calls them “community fish”. A peaceful species that is much larger or much faster can still make this shoal hide or lose condition.

Large or predatory fish, territorial cichlids, boisterous barbs, persistent fin nippers and aggressive feeders are poor choices. Bettas and gouramis vary by individual and can create both predation and feeding risks; they should not be treated as automatic companions. Angelfish and other large-mouthed fish can view tiny rasboras as prey even when they coexist with larger tetras.

Other small danionids and rasboras may be considered when their water, space and temperament requirements genuinely align. Customers comparing tiny Asian species can read the listings for the Emerald Dwarf Danio and Celestial Pearl Danio, but each species needs its own social group and sufficient space. The links are alternatives for research, not a promise that every combination fits one aquarium.

The Black Harlequin Rasbora and Harlequin Gold Rasbora are useful comparisons for keepers browsing rasboras, but they are larger-bodied fish with different space implications. Do not add them merely to create a mixed “rasbora school”. Assess the adult size, group requirements and total biological load of every species.

Shrimp, snails and bottom-dwelling fish

Adult dwarf shrimp can often coexist with these rasboras in a planted aquarium, but very small exposed shrimplets may be eaten. Dense moss and fine cover improve the shrimps’ chances without guaranteeing every offspring. Snails are normally ignored. Otocinclus should only be considered in a mature aquarium large enough for their own group and feeding needs; they cannot be added as a generic clean-up tool.

Preparing for delivery and introducing the shoal

Prepare the aquarium before the delivery day. Test the water, confirm the heater and filter are operating normally, protect intakes, and avoid major rescapes or filter replacement immediately before fish arrive. Have a clean container and the equipment required by the seller’s acclimation instructions ready. Keep aquarium lights subdued during introduction so the fish can settle without being chased through a brightly lit display.

On arrival, inspect the unopened bags promptly and follow the current live-arrival procedure supplied with the order. Do not place shipping-bag water into the aquarium unnecessarily. Temperature and chemistry differences both matter, so use an acclimation approach appropriate to the delivery conditions and retailer guidance rather than extending the process blindly. Once a transport bag is opened, the chemistry inside can change; longer is not automatically safer.

Release the group into prepared cover and give it time to orient. Do not judge final colour from the first minutes. Transport, lighting and a new background can temporarily reduce intensity. Offer only a small amount of suitable food after the fish are settled enough to respond, and avoid adding other livestock at the same time. Count the group, observe breathing and position, and recheck water if behaviour is unusual.

Quarantine and observation

A separate quarantine or observation aquarium can reduce the risk of introducing problems to an established community, but it must be suitable for tiny fish: cycled filtration, protected intake, stable heat, secure cover and appropriately sized food. Follow an established protocol rather than using an uncycled container. Never medicate automatically “just in case”; identify the problem, read the product instructions, account for invertebrates and seek experienced aquatic-veterinary guidance when necessary.

A routine that keeps the fish visible and feeding

Consistency is the goal. Carry out regular partial water changes suited to the stocking level and measured nitrate trend. Match replacement temperature and chemistry closely enough to avoid sudden change. During each maintenance session, inspect the intake guard, clear plant growth that blocks all swimming routes, and remove trapped organic waste from accessible areas without sterilising the aquarium.

Filter maintenance should restore flow while preserving biological media. Clean only what needs cleaning and avoid changing every media component at once. If flow has dropped, investigate clogged pre-filters and pipework before assuming a stronger pump is needed. After maintenance, confirm that the heater, filter and lid have been returned to safe positions.

Use a simple observation record if the aquarium is new to you. Note temperature, water-test results, water-change volume, appetite and any absent or isolated fish. Trends reveal more than a single perfect-looking test. A gradual change in feeding response or body condition can be detected sooner when normal behaviour is familiar.

1. Count the shoal and watch it before feeding.
2. Check temperature and inspect equipment.
3. Test water at a frequency appropriate to the tank’s age and stability.
4. Feed a small varied diet and confirm that all parts of the group gain access.
5. Perform measured partial water changes and targeted cleaning.
6. Recheck flow, lid security and fish behaviour after maintenance.

Recognising a problem early

A settled Neon Green Rasbora should be alert, balanced in the water, responsive to the group and able to feed. Its abdomen should not become persistently hollow, and breathing should not remain unusually rapid at rest. Colour alone is a weak diagnostic sign because it changes with light, background and stress. Combine appearance with behaviour, appetite, body condition and measured water results.

Warning signs include isolation from the shoal, loss of balance, repeated surface distress, clamped fins, visible spots or lesions, progressive weight loss, swollen tissues or failure to take correctly sized food. If several fish change at once, test temperature, ammonia, nitrite and other relevant parameters immediately and inspect equipment. If one fish is affected, water quality still needs checking, but individual injury or disease may require separate assessment.

Avoid random combinations of treatments. The wrong medication, dose or interaction can worsen stress, damage filtration or harm shrimp and snails. Move a fish only when the receiving tank is safe and the transfer has a clear purpose. Photographs, test results, onset timing and a list of recent additions help an experienced aquatic professional make a better assessment than a colour description alone.

Breeding overview

Microdevario kubotai is an egg-scattering species. In a densely planted, mature aquarium, well-conditioned adults may spawn among fine vegetation, but adults can consume eggs and very small larvae. A display tank may therefore produce an occasional survivor without producing a predictable number of young.

Keepers seeking a controlled result normally use a separate mature breeding aquarium with gentle filtration and very fine cover such as moss or spawning material. Mature females are generally fuller-bodied. Adults are conditioned with appropriately small nutritious foods, introduced without abrupt water changes, and removed after spawning if egg survival is the goal. Exact timing should not be promised because spawning and development vary with condition and temperature.

The difficult stage is feeding the tiny free-swimming young while protecting water quality. First foods must be small enough to take, filtration must not trap larvae, and maintenance must avoid both waste accumulation and sudden chemistry changes. Breeding should only be attempted when suitable grow-out space and a plan for the resulting fish already exist.

Neon Green Rasbora or Green Neon Tetra?

They are different fish. Neon Green Rasbora is the Asian danionid Microdevario kubotai. Green Neon Tetra is the South American characin Paracheirodon simulans. Both are small shoaling fishes and both can show green-blue iridescence, which explains the overlapping common-language searches, but their identity, distribution, body form and care context are not interchangeable.

Check the scientific name before buying. M. kubotai has a slender translucent yellow-green body with a golden-green lateral glow and clear fins. P. simulans has the recognisable tetra form and a blue-green iridescent stripe. This listing supplies Microdevario kubotai; repeated Green Neon Tetra care questions do not belong in its husbandry guide.

Is this the right fish for your aquarium?

Choose this species if you can provide a mature 54-litre-or-larger planted aquarium, a group of 10 or more, stable water within the stated range, gentle oxygenating flow and food small enough for every fish. It suits a keeper who enjoys observing subtle shoal behaviour and is willing to check body condition rather than assuming that all small fish find enough food.

Choose a different species or postpone the purchase if the aquarium is newly set up, the intended companions are large or forceful, the intake cannot be protected, or there is room for only a token group. Tiny adult size should not be used to justify unstable water or overcrowding. A well-planned shoal is bright, active and visible; a poorly matched group can become hidden and underfed.

When selecting the available dispatch size, remember that both options represent the same species and need the same adult plan. Review the current variant information at the buy box, then base the quantity on the social requirement and the tank’s verified capacity. Do not use an old price quoted in a care article; the live Shopify variant and checkout are the source for current price and availability.

A practical readiness audit before checkout

A good purchasing decision can be written down before fish are ordered. Start with the aquarium’s internal dimensions, not only the volume printed on its box. Record the existing fish and invertebrates, their adult sizes, their social-group requirements and where they feed. This reveals whether the proposed shoal has a genuine midwater route and fair access to food or whether the tank is already depending on optimistic stocking assumptions.

Next, use evidence from the aquarium itself. Review recent temperature and water-test results rather than relying on one reading taken for the purchase. Confirm that ammonia and nitrite have remained at zero during normal feeding, that the filter returns to full operation after maintenance, and that replacement water can be prepared consistently. If results vary unexpectedly, resolve the cause before adding more livestock. A delay is safer and less expensive than trying to stabilise the system around newly delivered fish.

Inspect physical risks at fish scale. Look through every filter slot, overflow, pipe gap and lid opening as though the fish were less than two centimetres long. Check whether floating plants can be pulled against an intake, whether a heater guard is needed, and whether the strongest current leaves a quieter feeding area. Place a tiny amount of the intended food into the running tank: it should remain accessible long enough to be eaten rather than disappearing immediately into filtration or beneath hardscape.

Define success before adding the shoal

Decide what will count as a successful introduction. Useful signs are the complete group remaining balanced in midwater, moving between cover and open space, responding to appropriately sized food, and maintaining body condition. Water tests and equipment should remain within their established pattern. Colour may strengthen as fish settle, but colour alone is not the measure of welfare and should never outweigh appetite, breathing, posture or group participation.

Also define the stop conditions. Do not add another species simply because the first group is visible, and do not increase feeding automatically because a few particles reach the bottom. Pause further stocking if any fish becomes persistently isolated, if food competition cannot be corrected, if ammonia or nitrite appears, or if flow and oxygenation change. Reassessing at that point protects the whole aquarium and prevents a small initial mismatch becoming a chronic problem.

• Write down the intended total of at least 10 before choosing the order quantity.
• Confirm the 54-litre-or-larger aquarium has useful length as well as nominal volume.
• Check recent water results, replacement-water preparation and equipment performance.
• Test lid gaps, intakes, flow and food movement at the fish’s actual scale.
• Prepare a quiet delivery-day plan and postpone other livestock additions.
• Set observable success and stop conditions for the introduction.

Research and further reading

This guide separates published species facts from conservative aquarium planning. The scientific name, family, recorded standard length and diagnostic appearance were checked against taxonomic databases and the original description. Practical aquarium recommendations were cross-checked against established UK care guidance and multiple real-image collections.

1. FishBase: Microdevario kubotai species summary — current classification, 1.9 cm standard length, morphology, distribution summary and conservation reference.
2. Kottelat and Witte (1999): original species description — “Two new species of Microrasbora from Thailand and Myanmar”.
3. GBIF: Microdevario kubotai — accepted-name and occurrence context, including the former combination.
4. Fishkeeper / Maidenhead Aquatics: Neon Green Rasbora — UK husbandry guidance covering a mature planted aquarium, a group of 10 or more, soft water and small foods.
5. iNaturalist: Microdevario kubotai — observation photographs and taxon context used as an additional appearance check.
6. FishBase species photographs — credited reference images used to check body shape, fins and natural colour variation.

Sources reviewed 3 August 2026. Aquarium care should also be adjusted to measured local water, tank dimensions, established livestock and the fish’s observed condition.