Rainbowfish care

Rainbowfish color up as they mature and settle, so a drab young fish in a shop often becomes a shimmering adult in a good group. The larger melanotaenias want room to swim, while blue-eyes and threadfins stay small enough for a nano tank. Each profile lists tank size and water conditions, and nearly every one gives a group size.

Tank size: 11–66 gal; 11 gal (40 L) to 66 gal (250 L); half the list needs 29 gal (110 L) or more
Temperature: 75–84°F; 24–29°C, most of the list
pH: 6.8–8.0; Most of the list
Difficulty: 17 easy; 47 medium · 1 difficult
Temperament: 62 peaceful; 3 mostly peaceful

65 species

Rainbowfish care

Rainbowfish are schooling fish and show their color in a group. Six is the minimum for most species, more is better, and several males per species is what turns on the display. They are active open-water swimmers, so tank length matters more than volume. The 3.9 to 5.9 inch (10 to 15 cm) melanotaenias want a 4 foot tank. Most of them list 30 to 53 gallons (115 to 200 liters) as a minimum. Most rainbowfish are undemanding about water and do well in neutral to moderately hard conditions, roughly pH 6.5–8.0 and 72–86°F (22–30°C). Boeseman's rainbowfish wants warmer water at 81–86°F (27–30°C), and the Sepik rainbowfish and the swamp and New Guinea blue-eyes start at 79°F (26°C). The desert rainbowfish goes down to 64°F (18°C), and the honey blue-eye to a pH of 5. Rainbowfish eat flake, pellets and frozen foods without fuss. Give them clear swimming room down the middle with planted edges, a lid because they jump, and time: a drab juvenile becomes a coloured adult over the first year, and the big species live five years or more.

Blue-eyes and threadfins for nano tanks

The blue-eyes (Pseudomugil) and the threadfin rainbowfish stay between 1.4 and 2.8 inches (3.5 and 7 cm). They are happy from 11 to 25 gallons (40 to 95 liters). They are gentle fish for gentle company: keep them with small, calm tankmates, feed fine foods such as baby brine shrimp and crushed flake, and give them floating plants or spawning mops to display over. Their lives are shorter than the big rainbows, which is one reason they are often bred at home. The Popondetta blue-eye is the easy one to start with; the forktail, red neon and spotted blue-eyes and the threadfin follow once the tank is settled.

Cool-water rainbows

Not every rainbowfish wants a tropical tank. The Australian rainbowfish, the Lake Kutubu and Lake Tebera rainbowfish and the Pacific blue-eye all list temperatures from around 68°F (20°C). The desert, Duboulayi's and ornate rainbowfish go lower still, to 64°F (18°C). The first four top out at 77–79°F (25–26°C), and a typical community tank runs at 75–80°F (24–27°C). They need the cool end of that range, an unheated room or a tank shared with other cool-water fish. The desert, Duboulayi's and ornate rainbowfish take the warm end as well. Check the temperature range on the profile before mixing them with warm-water species.

One species per tank if you want pure lines

Melanotaenia rainbowfish hybridise freely, and the offspring are fertile and hard to identify. Serious keepers run one species per tank or, at most, one species per genus. If you are not breeding them a mixed school is fine and looks good, but do not pass the fry on as a named species. The blue-eyes are a separate family and do not cross with the larger rainbows, and neither do the Madagascar and Celebes rainbowfish, which are here by name and habit; the Celebes rainbow is marked difficult and wants hard, alkaline water.

By the numbers

Smallest

Largest

Easiest to keep

Fits a 20 gallon tank

Fits a 30 gallon tank

FAQ

Common questions

How many rainbowfish should be kept together?

Six or more of one species for most rainbowfish, with several males. Most blue-eyes, the threadfin rainbowfish, the Celebes rainbow, the bonti sailfin silverside and the pygmy and Lake Furnusu rainbowfish want eight or more. The Wapoga rainbowfish wants ten or more and the Sahul rainbowfish a dozen. They school, and the males colour up when they have rivals to display to.

What size tank do rainbowfish need?

The 3.9 to 5.9 inch (10 to 15 cm) melanotaenias want a 4 foot tank. They list 30 to 53 gallons (115 to 200 liters) depending on species. Blue-eyes and threadfins are happy from 11 to 25 gallons (40 to 95 liters).

Why are my rainbowfish not colourful?

Age and company. Juveniles are drab, colour arrives over the first year, and males show it when there are other males to compete with. Colour is strongest in the morning and during displays. Poor water and a lone fish both dull it.

Are rainbowfish aggressive?

No, but they are boisterous. A large school of big melanotaenias can outcompete slow or long-finned fish at feeding time. Keep them with other active mid-water fish.

What do rainbowfish eat?

Flake and pellets as the staple, with frozen bloodworm, brine shrimp and daphnia. Blue-eyes and threadfins need finer food.

Can different rainbowfish species live together?

Yes, if they are a similar size and their temperature and pH ranges overlap. Boeseman's rainbowfish lists 81–86°F (27–30°C) and the Australian rainbowfish 68–77°F (20–25°C), so those two cannot share a tank. Keep blue-eyes and threadfins apart from the big melanotaenias, which outcompete them at feeding time. The catch is that melanotaenias interbreed, so keep one species per tank if you want to breed or sell pure fish.

Index