Scissortail Rasbora Care Guide

The scissortail rasbora is the classic sold-small-gets-big surprise — offered as a 2 to 3 cm juvenile, it grows into one of the largest commonly-sold rasboras at 13 to 15 cm. It is a fast, peaceful, open-water cruiser whose deeply forked black-and-yellow tail opens and closes like a working pair of scissors, and it needs a 4-foot tank, a tight lid, and tankmates too big to swallow.

Scissortail Rasbora at a glance

The sourced figures the welfare engine uses to judge Scissortail Rasbora — the parseable key facts.

Where it comes from

Rasbora trilineata ranges widely across south-east Asia — the Mekong and Chao Phraya basins, the Malay Peninsula, Sumatra and Borneo. Unusually for a rasbora it spans two very different waters: swiftly-flowing forest hill streams and sluggish blackwater peat swamps, and FishBase records it as a common resident of the surface waters of streams, canals and ditches. That generalist, ditch-and-stream heritage is why it is hardy and adaptable, forgiving of a broad parameter band as long as the water is stable and clean. The hill-stream side of its range means it appreciates some flow and a long open swimming lane rather than the still, shaded water a harlequin wants, and its wild surface orientation lines up with both its upper-water cruising and its strong jumping instinct.

Did you know?

• The name is a working pair of scissors — the deeply forked, black-and-yellow-barred tail opens and closes rhythmically as the fish hovers, a genuinely unusual, hypnotic motion among aquarium fish.
• It is a rasbora that ditches and canals call home — a common resident of the surface waters of Mekong and Chao Phraya streams, canals and ditches, far tougher and more adaptable than most delicate blackwater rasboras.
• At up to ~15 cm it is the giant of the common rasboras, dwarfing the harlequin (~4.5 cm) and the chili (~2 cm) — the sold-tiny-grows-big surprise in one fish.
• It spawns in the dark — FishBase notes it spawns only in darkened aquaria, a real breeding trigger rather than folklore.
• The scientific name and the trade name describe two different features: trilineata means 'three-lined' for the faint body stripes, while 'scissortail' is for the tail.
• It is assessed by the IUCN as Least Concern, widespread and popular in the aquarium trade, much of it now tank-bred.

Tank size — and why

This is a 13 to 15 cm fish, and the tank has to be sized for length, not gallons. Seriously Fish specifies a 48-inch (120 cm, around 255 litre / 67 US gallon) minimum because this is a fast open-water sprinter that needs a real swimming lane — a standard 30-gallon is only about 36 inches long and falls short on footprint even if the volume sounds adequate. Treat roughly a 48-inch, 55-gallon-plus tank as the true minimum for a proper group and a short 30-gallon as juvenile grow-out only. The driver is adult size, speed, group and open-water cruising, not bioload, so prioritise horizontal length over height every time.

As a guide, a 55-gallon tank comfortably suits about 6 Scissortail Rasbora as a single-species display, leaving room for tankmates.

How big does it really get?

Full-grown Scissortail Rasbora reach about 15 cm (5.9 in) long, but they are usually sold at only about 3 cm (1.2 in) — a typical shop size (estimate). At full size, Scissortail Rasbora needs roughly a 55-gallon tank, about 122 cm long; a common 10-gallon starter kit is only about 51 cm.

Adult size is sourced; the shop size is a typical-juvenile estimate; tank length is approximate for a standard 55-gallon aquarium.

Water parameters in practice

Hardy and adaptable, because its wild range runs from clear hill streams to acidic peat blackwater. Seriously Fish gives a wide tolerated pH of 5.0 to 8.0 depending on the fish's origin, with somewhere around 6.5 to 7.5 usually ideal, and it genuinely takes soft, acidic water as well as neutral. Hardness of about 2 to 12 dGH is comfortable. Temperature is the one to get right and a place sources are clear: FishBase gives 23 to 25 °C and Seriously Fish 22 to 25 °C, with care blogs at 23 to 26 °C — no reputable source recommends 28 °C for everyday keeping, so aim for 23 to 26 °C and treat the high-20s as a short-term breeding push only. As with any fish it dislikes unstable parameters and an uncycled tank more than any particular point in its broad range.

Diet & feeding

An insectivorous micropredator in the wild — it feeds mainly on insects, both aquatic and terrestrial, plus worms and crustaceans. In the tank it is an unfussy omnivore that readily takes good-quality flake and small pellet as the base; vary it with live and frozen daphnia, brine shrimp, bloodworm and mosquito larvae for best colour and breeding condition. Feed small amounts one to three times a day, only as much as is eaten in a few minutes. It is a fast, confident mid-to-upper-water feeder that darts for food and easily out-competes shy or slow tankmates, so make sure bottom-dwellers get their share. That same insect-and-crustacean instinct is why a grown scissortail treats baby shrimp and bite-size fry as food.

Gear & setup

Set the tank up for a fast cruiser: a long footprint with open central swimming space, planting kept to the back and sides, and darker substrate with some shade to improve colour and confidence (the peat-swamp side of its range). A tight-fitting lid is not optional — this is an accomplished jumper that will leap out of an uncovered tank, and a loose lid is the single most preventable cause of death. A heater holds the stable low-to-mid-20s setpoint, and unlike most slow-water rasboras it tolerates and enjoys moderate flow, so a filter giving some current suits the hill-stream side of its nature.

Temperament & behaviour

Peaceful by temperament — very peaceful indeed, and a thoroughly peaceful community fish toward equals, with no territoriality, fin-nipping or same-species aggression. The catch is mouth-size, not temper: a 13 to 15 cm fish will opportunistically pick off baby shrimp and anything small enough to swallow even though it is not predatory in disposition. It is an active open-water schooler that occupies the upper and middle column, and the behaviour transforms with numbers and space — a big group in a long tank settles into calm, dazzling synchronised cruising, while a few fish in a short tank turn nervous, jumpy and flight-prone.

Group & social needs

Keep a real group. Six is the floor and only in a 48-inch tank; eight or more is better. Kept in twos and threes a large, fast schooler turns nervous and skittish and jumps more, while a proper group settles it into confident open-water cruising. Buy eight as the target and never fewer than six.

Compatible tank mates (preview)

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

• Boesemani Rainbowfish — Peaceful temperament, similar adult size.
• Bolivian Ram — Uses the bottom zone, peaceful temperament, similar adult size.
• Brilliant Rasbora — Peaceful temperament, similar adult size.

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

Breeding & sexing

An egg-scattering, continuous spawner with no parental care — moderate difficulty, harder than livebearers but easier than the harlequin's specialised leaf-spawning. FishBase notes it spawns only in darkened aquaria and deposits adhesive eggs on the bottom, so it sits somewhere between a free-scatterer and a substrate-depositor. Sexing is subtle and reliable only on conditioned adults: mature females are noticeably rounder-bellied and a little larger, males slimmer and sometimes more intensely marked. To breed, use a separate dimly-lit spawning tank of 20 gallons or more with a mesh grid or fine-leaved plant base to protect the eggs, condition the group heavily on live food, and trigger with soft, slightly acidic water warmed to about 26 to 28 °C. Eggs hatch in roughly 18 to 48 hours and the fry are free-swimming two to three days later; remove the adults, which eat eggs and fry, and start the fry on infusoria then newly-hatched brine shrimp.

Lifespan

About five years is the central estimate, with seven years commonly cited under good care and exceptional fish reported to ten. Treat ten as a rare ceiling, not an expectation. What shortens it is chronically warm water kept at the top of the range, too small a tank or group for a fast schooler, unstable water quality, and the slow stress and injury of jumping in an under-covered tank.

Common mistakes

• Buying it for a small tank because it looks small in the shop. It is a 13 to 15 cm fish needing a 48-inch (~55-gallon-plus) tank — the number-one mistake.
• No lid, or a loose one. An accomplished jumper; carpet deaths are common and entirely avoidable with a tight cover.
• Too small a group. One to five fish turn nervous, jumpy and faded; buy six at minimum and eight or more for a settled, synchronised shoal.
• Housing it with bite-size tankmates. Despite the 'peaceful' label, a grown scissortail eats baby shrimp and shrimp/fish fry and stresses true nano fish with its constant fast swimming — keep it away from dwarf-shrimp colonies, Boraras, chili rasboras and fry.
• Running it too warm. No source recommends 28 °C for maintenance; aim 23 to 26 °C and save the high-20s for breeding.
• Assuming 'peaceful' means 'safe with everything'. It is peaceful toward equals but predatory by mouth-size toward the very small.

Signs of trouble

• Persistent skittish dashing and jumping — often a too-small-group or too-short-tank stress signal rather than illness, and the prelude to a fish on the floor.
• Colour fading, clamped fins and a fish dropping out of the shoal — general stress, frequently from an immature tank or cramped quarters.
• Flicking and scratching against decor — early ich (white spot), the usual stress and new-tank disease.
• Loss of appetite and hiding in an otherwise bold open-water fish — investigate water quality before it progresses.

Is this fish right for you?

Don't buy scissortail rasboras if you only have a tank under about 48 inches, can't keep a group of six to eight or more, can't fit a tight lid, or run a shrimp-breeding, nano-fish or fry setup they would pick off. It is hardy and adaptable, so the trap is never the fish's toughness — it is buying a 13 to 15 cm open-water sprinter, sold tiny, into a tank too short and too open-topped for it. Skip any tank holding faded, curved or scratched-looking fish, and don't confuse it with the larger Rasbora caudimaculata (greater scissortail) sometimes sold under overlapping names.

Bringing one home

Float the bag to equalise temperature, then add tank water gradually over fifteen to twenty minutes before netting the fish across into a mature, cycled tank and leaving the transport water behind. It is hardy and adaptable, so acclimation is less fraught than for a soft-water specialist, but settle the fish into a covered tank — a freshly-moved, nervous scissortail is at its most jump-prone in the first days. Quarantine new arrivals to protect the group.

Common questions

How big do scissortail rasboras get and what tank do they need?

They reach about 13 to 15 cm — one of the largest commonly-sold rasboras, despite being sold as 2 to 3 cm juveniles. They need a 48-inch tank (around 55 gallons or more) for the swimming length a fast open-water schooler requires; a short 30-gallon is grow-out only. Buy for length, not gallons.

Are scissortail rasboras safe with shrimp and small fish?

Adult shrimp are usually safe, but a grown 13 to 15 cm scissortail picks off baby shrimp and bite-size fry, and stresses true nano fish with its constant fast swimming. It is peaceful by temperament but predatory by mouth-size, so keep it away from dwarf-shrimp colonies, Boraras, chili rasboras and fry.

Do scissortail rasboras jump?

Yes — they are accomplished jumpers and will leap from an uncovered tank. A tight-fitting lid is mandatory and is the single most effective way to prevent the most common cause of death in this fish.

How many scissortail rasboras should I keep, and at what temperature?

Six is the bare minimum and only in a 48-inch tank; eight or more is better and keeps the school calm and synchronised rather than jumpy. Keep them at 23 to 26 °C — no reputable source recommends 28 °C for everyday maintenance, which is a breeding push only.

Why is it called a scissortail?

Its deeply forked caudal fin carries a black bar tipped with yellow or white on each lobe, and the lobes open and close in a rhythmic twitching motion so the tail looks like a working pair of scissors, most obvious when the fish hovers or swims slowly.

Sources & confidence

Sources & confidence (9 species)

These back the Scissortail 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.

• Scissortail Rasbora Rasbora trilineata — Seriously Fish (seriouslyfish.com/species/rasbora-trilineata) high confidence
• Boesemani Rainbowfish Melanotaenia boesemani — Seriously Fish; Aquarium Co-Op Boesemani guide high confidence
• Bolivian Ram Mikrogeophagus altispinosus — Seriously Fish (seriouslyfish.com/species/mikrogeophagus-altispinosus) high confidence
• Brilliant Rasbora Rasbora einthovenii — Seriously Fish (seriouslyfish.com/species/rasbora-einthovenii) high confidence
• Bristlenose Pleco Ancistrus sp. — Aquarium Source / aqua-fish.net Ancistrus care guides high confidence
• Clown Pleco Panaqolus maccus — Fish Laboratory (fishlaboratory.com/fish/clown-pleco); AquariumStoreDepot high confidence
• Congo Tetra Phenacogrammus interruptus — Seriously Fish (seriouslyfish.com/species/phenacogrammus-interruptus) high confidence
• Dwarf Gourami Trichogaster lalius — Seriously Fish (seriouslyfish.com/species/trichogaster-lalius) high confidence
• Gold Barb Barbodes semifasciolatus — Fishlore gold barb profile / FishBase Barbodes semifasciolatus high confidence

Care-guide sources (6)

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 — Rasbora trilineata — authority (Steindachner 1870), family Danionidae, max 13.0 cm TL, temp 23-25 C, pH 6.0-8.0, dH 5-12, range (Mekong & Chao Phraya basins; Malay Peninsula, Sumatra, Borneo), habitat (lakes/swamps/slow rivers; surface waters of streams/canals/ditches), diet (exogenous insects, worms, crustaceans), spawns only in darkened aquaria / adhesive eggs on bottom, IUCN Least Concern
• Seriously Fish — Rasbora trilineata — fully-grown ~6 in/15 cm, min tank 48x18x18 in / 255 L (~67 gal), temp 22-25 C, pH 5.0-8.0 (ideal 6.5-7.5), hardness 2-12 dH, dual habitat (hill streams + peat blackwater), diet, 'very peaceful', group at least six, surface-dweller, 'accomplished jumper' needing tight cover, egg-scattering continuous spawner with no parental care, eggs hatch 18-48 h, sexing (females rounder/larger)
• AquariumStoreDepot — Scissortail Rasbora Care Guide — max 5 in/13 cm (typ 4-4.5 in), lifespan 5-8 yr, 30 gal min + prioritise horizontal length, temp 73-78 F/23-26 C, pH 6.0-7.5, mid-to-top swimmer, group 6 (8+ better), known jumper / tight lid essential, scissoring-tail description, 'baby shrimp may be picked off', nano fish stressed by its speed, breeding (egg scatterers, ~24-48 h hatch, remove adults)
• AquariumSource — Scissortail Rasbora Care — typ 3.5 in (to ~6 in), lifespan ~5 yr (to 7+), 20 gal min (30 better), 73-78 F, pH 6.0-7.0, 2-12 dGH, diet & feeding 3x/day, peaceful, group 6, upper-and-middle swimmer, jumping/lid, breeding 'medium', common mistakes
• Fish Laboratory — Scissortail Rasbora Ultimate Care Guide — size 5-6 in (8 in outlier reported and rejected), lifespan 5 yr (to 10), 20 gal+, 72-79 F/22-26 C, pH 6.6-7.0, 2-15 dH, peaceful, group 5-6, jumping/lid, scissoring-tail etymology ('opens and closes like a pair of scissors'), 'three-lined' name
• Shrimpy Business — Scissortail Rasbora Size & Care — up to 3.5 in, lifespan 3-5 yr, peaceful, group 6, top-dwelling, 20 gal min (long > tall), prone to jumping / tight lid, omnivore diet

More on Scissortail 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 →