Rasbora is not one genus, it is at least seven
The word on the shop label covers fish from several genera, sizes from half an inch to six, and tanks from three gallons to fifty five. Read a rasbora care sheet without the species name and it is describing an animal that may not be the one in the bag.
Aquarium Co-Op says it in the first line of its own list: the common name rasbora actually refers to several genera of fish, including Rasbora, Boraras, Trigonostigma, Microdevario, and many more. It describes the group as schooling fish with torpedo-shaped bodies and peaceful personalities, mostly from Southeast Asia.
Wikipedia gives the genus proper: over 80 species, native to freshwater habitats in South and Southeast Asia as well as southeast China, up to 17 cm, 6.7 in, long, although most species do not surpass 10 cm, 4 in, and many have a dark horizontal stripe.
It also gives the reason the common name is so loose. In a 2007 analysis, Rasbora was found to not be a monophyletic assemblage, while Boraras and Trigonostigma were determined to be monophyletic, and it names Brevibora, Megarasbora, Microdevario and Microrasbora among the genera called rasboras colloquially that were historically included in Rasbora.
So the two most useful fish under this name are not in the genus it comes from. Our own chili rasbora record is Boraras brigittae, and the harlequin, the one source we cite calls a classic beginner fish, is a Trigonostigma.
What this guide is
- The question
- Four thousand eight hundred searches a month for the group, and another seven thousand across ten species names.
- Why it is filed here
- Under stocking, because the group figures our two list sources publish for the same fish differ by a factor of two and a half.
- The record behind it
- Our chili rasbora record, which is the only rasbora written here and the one whose four sources split two against two on pH.
The ten rasboras one source publishes figures for
Aquarium Co-Op is the only source we hold that gives a figure for every fish on its list. This is that list, unaltered.
| Species | Size | Temperature | pH | Tank and group |
|---|---|---|---|---|
| Harlequin | 2 in | 72 to 82 °F | 6 to 8 | Not stated. Called a classic beginner fish |
| Chili | 0.75 in | 72 to 82 °F | 6 to 8 | 3 to 5 gal, group of 8 to 12 |
| Green neon or kubotai | 0.75 in | 72 to 80 °F | 6 to 7 | 5 gal or larger, group of 8 to 12 |
| Scissortail | 4 to 5 in | 73 to 77 °F | 6 to 8 | At least 4 feet in length |
| Asian rummy-nose | 1.25 in | 68 to 77 °F | 7 to 8 | 10 gal or more |
| Clown | 2 to 3 in | 75 to 82 °F | 5.0 to 7.5 | At least 3 feet in length |
| Brilliant | 2 to 2.5 in | 72 to 79 °F | Below 7.0 | A 30 inch aquarium or larger |
| Blue neon or blue axelrodi | Under 1 in | 73 to 79 °F | Acidic | 5 to 10 gal or bigger, group of 8 to 12 |
| Galaxy | 1 in | 72 to 76 °F | 6.6 to 8.0 | 10 or 20 gal, group of 10 to 15. Called shy |
| Emerald dwarf | 1 to 1.25 in | 70 to 77 °F | Neutral to alkaline | 10 to 20 gal |
Read the size column and the word rasbora stops being a description. Under an inch for the blue axelrodi and four to five inches for the scissortail, with tanks running from three gallons to a four foot aquarium. Our tetra fish guide found the same spread under one word, and the same conclusion applies: the group figure is not a species figure.
Two of the ten are the ones people actually buy, and they are at opposite ends of the table. The harlequin is the one Aquarium Co-Op calls a classic beginner fish, at 2 inches in water it puts at 72 to 82 °F and pH 6 to 8. The chili is a 0.75 inch fish that the same source will keep in three to five gallons.
Note what the table does not have. Aquarium Co-Op publishes a group size for only four of its own ten, and a tank size in inches or feet rather than gallons for three of them, which is a footprint instruction wearing a length.
The same species, two sets of numbers
Aquarium Store Depot lists eleven rasboras with its own figures. Where the two lists overlap, they do not agree.
| Species | Aquarium Co-Op | Aquarium Store Depot | The gap |
|---|---|---|---|
| Harlequin | 2 in, 72 to 82 °F, pH 6 to 8 | 1.5 to 1.75 in, 70 to 82 °F, pH 5.5 to 7.5, 10 gal with 20 recommended, group of 8 or more | A quarter inch of size and half a point of pH at each end |
| Chili | 0.75 in, pH 6 to 8, 3 to 5 gal, group of 8 to 12 | 0.75 in, pH 4 to 7, 10 gal, group of 6 or more | The pH ranges meet from 6 to 7 and the tanks differ by a factor of three |
| Green kubotai | 0.75 in, 72 to 80 °F, pH 6 to 7, 5 gal or larger | 0.75 in, 68 to 80 °F, pH 6 to 7, 15 gal | Same fish, same pH, and three times the tank |
| Blue axelrodi | Under 1 in, pH acidic, 5 to 10 gal, group of 8 to 12 | 0.75 in, pH 4 to 6.5, 5 gal, group of 20 or more | The group figure differs by a factor of two and a half |
| Dwarf emerald | 1 to 1.25 in, 70 to 77 °F, neutral to alkaline, 10 to 20 gal | 1 in, 68 to 75 °F, pH 7.5 to 8, 10 gal, group of 6 or more | One source gives figures where the other gives an adjective |
| Scissortail | 4 to 5 in, 73 to 77 °F, pH 6 to 8, at least 4 feet long | 6 in, 73 to 77 °F, pH 6.5 to 7.5, 55 gal | An inch to two inches of adult size, on the largest fish on either list |
The chili row is the one this site can check, because we hold the record. Our chili rasbora record carries four sources that split exactly the way these two do: Seriously Fish and Aquarium Source give pH 4.0 to 7.0, Aquarium Co-Op and Wikipedia give 6.0 to 8.0, and the record prints the 6.0 to 7.0 the two pairs share. The two group lists here reproduce that split without either of them mentioning it.
The kubotai row is the one worth pausing on for a buyer. Five gallons or fifteen, for the same 0.75 inch fish, from two sources that both sell it. Nothing in either page explains the difference, and on a nano fish that is the whole decision.
And the family the fish belong to is not agreed either. Wikipedia places the genus in Danionidae; Aquarium Store Depot describes rasboras as freshwater fish from the Cyprinidae family. Danionidae was split out of Cyprinidae, so the older placement is not wrong so much as superseded, which is exactly what our tetra fish guide found when the tetra families were split out of Characidae in 2024. Nothing about keeping them changes; a reader who looks the family up finds a different answer from the one the hobby gives.
How many rasboras make a school? Six, eight, ten, or twenty
Every group figure our sources publish
- Six or more: Aquarium Store Depot, for the chili and the dwarf emerald.
- Eight or more: Aquarium Store Depot, for the harlequin and the green kubotai.
- Eight to twelve: Aquarium Co-Op, for the chili, the green neon and the blue axelrodi.
- Ten: Aquarium Store Depot, for the spotted or dwarf rasbora.
- Ten to fifteen: Aquarium Co-Op, for the galaxy rasbora, which it also calls shy.
- Twenty or more: Aquarium Store Depot, for the blue axelrodi, the same fish Aquarium Co-Op puts at eight to twelve.
Six of the ten species on the first list get no group figure at all, including the harlequin, which is the one most people buy.
What the numbers are for
Aquarium Store Depot gives the reason behind the largest figures: the smallest species need large numbers to show personality, and they are shy by nature without dense planting. Aquarium Co-Op calls the galaxy rasbora shy in the same breath as asking for ten to fifteen of them.
Our own record turns that into a figure a keeper can act on. Our chili rasbora record carries Seriously Fish asking for 8 to 12 specimens, and the same source’s instruction that a group is what makes the fish visible rather than hidden. It also carries the sentence neither group list prints: do not introduce any Boraras species to a biologically-immature aquarium.
So the honest answer to how many is a species answer with a floor: nothing our sources publish asks for fewer than six of any rasbora, and the two figures for the smallest fish here run from eight to twenty. Our stocking page is where this site keeps the arithmetic those lists leave out, and our stocking calculator works from the one rasbora record we hold.
The care that does not change with the species
The food
Aquarium Co-Op’s harlequin guide is the one source we hold that publishes a diet for a rasbora, and it is short: these fish are omnivorous, prepared flake food is one of your best food options, and it names daphnia, mosquito larvae and brine shrimp among the live foods.
Our own chili rasbora record is stricter, because the fish is smaller: it carries sources asking for food sized for a nano fish or crushed to fit, which is the instruction a flake tin does not come with.
The temperament
Aquarium Co-Op describes the group as schooling fish with peaceful personalities and the harlequin specifically as having docile temperaments, adding that they are a bit timid and might swim away if you approach the tank. On tank mates it says harlequins happily coexist with bettas and different types of tetras, including neon, cardinal and black phantom tetras.
That betta line is worth flagging against our own records. Our betta record carries one source that will not put a betta in a community tank at all against another naming five tank mates, so a recommendation in one direction does not settle it.
The planted tank, which both sources ask for
Aquarium Co-Op: their colors really pop out against the waving greenery, and these fish are not really that into swimming amongst plastic plants, so you really want the real live plants. Aquarium Store Depot puts it as a warning instead: the smallest species are shy by nature without dense planting.
Both statements point at the same thing, and it is the reason the group figures in station 04 matter: a shy schooling fish in an open tank is a fish you have bought and cannot see. Our plants silo holds four records, and the two our fish records name most often, java moss and java fern, are both named on our chili rasbora record by their scientific names.
The harlequin, and a source disagreeing with itself
Aquarium Co-Op’s species page gives the harlequin an optimal water tank temperature of around 76 degrees Fahrenheit, a pH of approximately 7.2, relatively soft water, and a school of six in at least a 10 gallon, warning that in smaller schools, these fish will stress.
Its own top ten list gives the same fish 72 to 82 °F and pH 6 to 8 and no group figure at all. One page prints a target and the other prints a tolerance, which is the distinction our betta record makes in its temperature row and the one most care sheets skip.
On the marking that names the fish: a distinct darker black mark starting in the mid-belly and extending back towards the tail. The lambchop and espei rasboras differ from it in color rather than shape, with the harlequin having more of a pinkish brown tone and the lambchop a brighter orange.
Rasbora tank mates, and the four records our sources name
One source publishes a tank mate list for the group. Read against our own records it is unusually clean, because a peaceful nano fish in soft water fails on almost nothing here.
Aquarium Store Depot names smaller corydoras catfish, kuhli loaches, dwarf gouramis, cardinal tetras, shrimp and snails, and adds the one exception on the page: the smallest Boraras species do best in a species-only tank.
- Our corydoras record covers the pygmy species by name, at 72 to 82 °F and pH 6.5 to 7.8, which contains most of the rasbora figures in station 02.
- Our kuhli loach record carries 74 to 79 °F and pH 3.5 to 7.0, the softest, most acid range on this site, which suits the Boraras end of this group better than anything else we hold.
- Our honey gourami record is the dwarf gourami our sources mean, and our gourami fish guide explains why the two are not the same fish: the dwarf gourami is a different species that three sources call more prone to bullying.
- Our ember tetra record is not the cardinal tetra, but it is the tetra on this site whose water sits where a rasbora is published for, pH 5.5 to 7.0.
On shrimp the group list and our records agree, which is rare. Aquarium Store Depot puts shrimp on the safe side, and our chili rasbora record carries Aquarium Co-Op naming amano and cherry shrimp among its tank mates. Our tank mates grid holds no refusal against that record at all.
The species-only exception is the one to take seriously, because it applies to the fish this site holds a record for: Boraras brigittae is a Boraras, and our own record carries Seriously Fish saying it does not make an ideal community fish due to its small size and rather timid nature, against Aquarium Co-Op calling it refreshingly bold. That disagreement is printed on the record and neither group list mentions it.
What this guide will not answer
Which figures are right
Two sources list the same six species and disagree about size, pH, tank size or group on every one of them. We print both columns and the gap.
What a rasbora is, taxonomically
Several genera per one source, over 80 species in the genus proper per another, and a family that is Danionidae in one place and Cyprinidae in another.
How many for the harlequin
Eight or more per Aquarium Store Depot. Aquarium Co-Op publishes no group figure for the fish it calls a classic beginner fish.
Lifespan or hardness for any of them
None of our four sources publishes a lifespan for any species, and none publishes a hardness number: the closest is the harlequin guide asking for relatively soft water without saying how soft. That is why this is a guide rather than a set of records.
The species with no figures anywhere
Brilliant, exclamation point, emerald eye and merah rasboras appear on one list each with partial figures. Nothing we hold covers them the way a record would. The espei came off this list with the fourth source, which covers it alongside the harlequin.
Whether your rasbora is the fish on the label
Aquarium Co-Op says the name covers several genera and many more besides. No source we hold gives a way to tell one small striped rasbora from another.
Rasbora questions, answered from the sources
What is a rasbora?
A common name rather than a genus. Aquarium Co-Op: the common name rasbora actually refers to several genera of fish, including Rasbora, Boraras, Trigonostigma, Microdevario, and many more. Wikipedia gives the genus proper as over 80 species from South and Southeast Asia and southeast China, up to 17 cm long, with most species not surpassing 10 cm, and notes that a 2007 analysis found Rasbora not to be a monophyletic assemblage.
How many rasboras should be kept together?
Six at the least and twenty at the most, depending on the species and the source. Aquarium Store Depot asks for six or more for the chili and dwarf emerald, eight or more for the harlequin and kubotai, ten for the spotted, and twenty or more for the blue axelrodi. Aquarium Co-Op asks for eight to twelve for the chili, green neon and blue axelrodi and ten to fifteen for the galaxy. That last pair is the same fish at eight to twelve and twenty or more.
What size tank do rasboras need?
Three gallons to fifty five, and the species decides. Aquarium Co-Op will keep chili rasboras in 3 to 5 gallons and asks for at least a four foot tank for the scissortail. Aquarium Store Depot asks for 10 gallons for most of its list, 15 for the green kubotai, and 55 for the scissortail. Where the two overlap they disagree by up to a factor of three.
What do rasboras eat?
Aquarium Co-Op’s harlequin guide is the only source we hold with a diet: these fish are omnivorous, prepared flake food is one of your best food options, and it names daphnia, mosquito larvae and brine shrimp among the live foods. Our chili rasbora record is stricter because the fish is smaller, asking for food sized for a nano fish or crushed to fit.
What temperature do harlequin rasboras need?
Aquarium Co-Op publishes two answers on two of its own pages. Its harlequin guide gives an optimal temperature of around 76 °F with a pH of approximately 7.2 in relatively soft water; its top ten list gives the same fish 72 to 82 °F and pH 6 to 8. One is a target and the other is a tolerance, and neither page says so.
Are rasboras schooling fish?
Both of our list sources describe them as schooling fish, and Aquarium Store Depot adds the reason the numbers matter: the smallest species need large numbers to show personality and are shy by nature without dense planting. Aquarium Co-Op calls the galaxy rasbora shy while asking for ten to fifteen of them.
What is the easiest rasbora to keep?
The harlequin, on the only verdict either source gives. Aquarium Co-Op calls it a classic beginner fish with a hardy constitution, at 2 inches, 72 to 82 °F and pH 6 to 8. Aquarium Store Depot gives the same fish as 1.5 to 1.75 inches at pH 5.5 to 7.5 in a 10 gallon with 20 recommended, and asks for eight or more.
What is the difference between a rasbora and a tetra?
Geography and family. Rasboras are from South and Southeast Asia, per Wikipedia, while our tetra fish guide covers South American and African fish. Aquarium Store Depot says directly that rasboras are not tetras despite the similarities. Both groups are small schooling fish sold under a name that covers several genera, and both have the same problem: the group figure is not a species figure.
What are good rasbora tank mates?
Aquarium Store Depot names smaller corydoras catfish, kuhli loaches, dwarf gouramis, cardinal tetras, shrimp and snails, and adds that the smallest Boraras species do best in a species-only tank. We hold records for four of those groups, and our chili rasbora record carries Aquarium Co-Op naming amano and cherry shrimp among its tank mates. That record has no refusal against it on our grid.
What water do rasboras need?
Soft and warm, and the figures depend on which fish. Across the ten species Aquarium Co-Op publishes, the temperatures run from 68 to 82 °F and the pH from acidic to 8.0. Aquarium Store Depot goes further down, to pH 4 for three of the Boraras species. No source here publishes a hardness number, the harlequin guide asking only for relatively soft water, which is why our chili rasbora record is the only place on this site with a hardness figure for a rasbora, 54 to 179 ppm.
How big do rasboras get?
From under an inch to six inches. The blue axelrodi is under 1 inch per Aquarium Co-Op and the scissortail is 4 to 5 inches on the same list, or 6 inches per Aquarium Store Depot. Wikipedia gives the genus proper as up to 17 cm, 6.7 in, with most species under 10 cm. The chili rasbora on our own record tops out at 20 mm.
Which rasbora is the smallest?
The blue axelrodi and the chili, both under an inch on both lists, with Aquarium Store Depot giving the exclamation point rasbora at 0.5 to 0.7 inches, which is the smallest figure either source publishes. Our chili rasbora record carries 0.7 to 0.8 in and ties our ember tetra and least killifish records for the smallest fish on this site.
What family are rasboras in?
Our sources disagree, and it is the same drift our tetra guide found. Wikipedia places the genus Rasbora in Danionidae. Aquarium Store Depot describes rasboras as freshwater fish from the Cyprinidae family. Danionidae was split out of Cyprinidae, so the older placement is superseded rather than wrong, and nothing about keeping them changes either way.
Can rasboras live with shrimp?
Our sources say yes for the group. Aquarium Store Depot puts shrimp on its compatible list, and our chili rasbora record carries Aquarium Co-Op naming amano and cherry shrimp among its tank mates. That is a rare agreement on this site, where most fish records carry a shrimp warning of some kind.
Why does this site have only one rasbora record?
Because a record here carries nine fields with a source behind each, and none of our four sources publishes hardness or lifespan for any species. Our chili rasbora record exists because four sources cover that one fish in enough detail to fill the table, and the harlequin rasbora is one of the names in the queue on our freshwater fish silo.