There are over 100 rainbowfish species, but the types of rainbow fish you will actually find for sale come down to about a dozen, sorted into three size bands: the dwarf species under 2.5 inches (dwarf neon, threadfin, forktail, Gertrude's blue-eye), the medium 3–4.5 inch Melanotaenia that make up most of the hobby (boesemani, turquoise, neon-blue, celebes), and the large 4–6 inch species (Australian, splendid, red, parkinson's). The band tells you the tank; the species tells you the colour; and the care is the same recipe for all of them — a school of six or more, a long tank and hard water.
The Three Groups of Rainbow Fish
- Dwarf rainbowfish and blue-eyes (Melanotaenia praecox, Iriatherina, Pseudomugil) — 1.5–2.5 inches, schools of 8–10, 20–30 gallon tanks, small food. The threadfin and blue-eyes are technically a sister family but are sold and kept as rainbowfish.
- Medium Melanotaenia — the classic community rainbowfish at 3–4.5 inches: boesemani, turquoise (Lake Kutubu), neon-blue, celebes (Marosatherina). Schools of 6–8 in 40–55 gallons.
- Large Melanotaenia and Glossolepis — Australian, splendid (eastern), parkinson's and the red rainbowfish, 4–6 inches, 55–75 gallon tanks. The hardiest of all types of rainbow fish.
Types of Rainbow Fish Compared
| Rainbowfish | Scientific name | Size | Min. tank | Colour | Hardiness |
|---|---|---|---|---|---|
| Boesemani | Melanotaenia boesemani | 4 in | 40 gal | Blue front, orange rear | Very hardy |
| Dwarf neon | Melanotaenia praecox | 2.5 in | 20 gal | Violet-blue, red or yellow fins | Hardy once settled |
| Turquoise / Lake Kutubu | Melanotaenia lacustris | 4.5 in | 40–55 gal | Electric blue-green | Very hardy |
| Neon-blue / Lake Kutubu blue | Melanotaenia sp. | 3.5 in | 40 gal | Steel blue with a dark stripe | Hardy |
| Australian | Melanotaenia fluviatilis | 4–5 in | 55 gal | Silver-green with red bars | The hardiest |
| Splendid / eastern | Melanotaenia splendida | 4–5 in | 55 gal | Yellow, red and blue chequering | Very hardy |
| Parkinson's | Melanotaenia parkinsoni | 5 in | 55–75 gal | Orange-gold rear half | Hardy |
| Red (salmon-red) | Glossolepis incisus | 5–6 in | 75 gal | Solid red males | Hardy |
| Celebes | Marosatherina ladigesi | 3 in | 30 gal | Yellow fins, blue line | Delicate; small food |
| Threadfin | Iriatherina werneri | 1.5–2 in | 20 gal | Trailing black fins | Delicate; powdered food |
| Forktail blue-eye | Pseudomugil furcatus | 2 in | 20 gal | Yellow fins, blue eyes | Moderate |
| Gertrude's spotted blue-eye | Pseudomugil gertrudae | 1.5 in | 15–20 gal | Spotted fins, blue eyes | Moderate; short-lived |
Sizes and ranges follow the family account on Wikipedia's rainbowfish page. Minimum tanks are for a school of six (eight for the dwarf species); the rainbow fish tank size page explains the length behind each figure.
Medium Types of Rainbow Fish: Boesemani, Turquoise and Celebes
The boesemani rainbowfish is the most popular of all types of rainbow fish and for good reason: hardy, peaceful, 4 inches, and the only common freshwater fish that is two colours at once — blue-purple at the front, orange-yellow at the back. It takes a year to colour up and lives ten. The full profile is on the boesemani rainbowfish care page. The turquoise rainbowfish from Lake Kutubu is the same size and temperament in electric blue-green, arguably the most intense blue in freshwater, and the two species are the classic pair for a 75-gallon tank. The neon-blue is a smaller, steel-blue Kutubu relative. The celebes rainbowfish from Sulawesi is a different family, more delicate, at 3 inches with yellow fins and a blue lateral line; it needs small food, very stable water and a calmer tank than Melanotaenia.
Large Types of Rainbow Fish: Australian, Splendid and Red
The large species are the toughest fish in the family and the best choice for a 4-foot tank in a hard-water area. The Australian rainbowfish (M. fluviatilis, and its close relative the crimson-spotted M. duboulayi) tolerates the widest temperature range of any rainbowfish, from 68 to 82°F, and lives 6–8 years. The splendid or eastern rainbowfish comes in a dozen regional colour forms with chequered yellow, red and blue. Parkinson's males develop a glowing orange rear half. The red rainbowfish (Glossolepis incisus) from Lake Sentani is the largest at 5–6 inches and the only one where a dominant male is solid red from nose to tail; the females are olive, and the red only appears in a school with two or more males competing. All four need 55–75 gallons and 4 feet. Profiles: Australian rainbowfish.
Dwarf Rainbowfish: Dwarf Neon, Threadfin and Blue-Eyes
The dwarf neon rainbowfish (M. praecox) is the small tank's rainbowfish: 2–2.5 inches, violet-blue with red (male) or yellow (female) fins, 8–10 in a 20-gallon long. It runs warmer than the rest of the genus and ships badly, so it goes into a mature tank after quarantine; profile on the dwarf neon rainbowfish care page. The threadfin rainbowfish is the most beautiful of the tiny species, with black, thread-like trailing fins on the males, and the most demanding: 1.5 inches, powdered or live food only, no boisterous tank mates, and a short life of three to four years. The forktail blue-eye and Gertrude's spotted blue-eye (Pseudomugil) are 1.5–2 inch nano-tank fish with luminous blue eyes and yellow or spotted fins, best in species tanks of ten or more with floating plants. Profile: threadfin rainbowfish.
Best Rainbow Fish for Beginners and for Colour
- Boesemani — hardy, 40 gallons, the two-tone colour, ten-year lifespan. The default first rainbowfish.
- Australian rainbowfish — the toughest, widest temperature range, 55 gallons.
- Turquoise rainbowfish — as hardy as boesemani and the best blue; 40–55 gallons.
- Dwarf neon — the pick for a 20-gallon long, once the tank is mature.
- Red rainbowfish — the most dramatic, if you have a 75.
Save the threadfin, celebes and Madagascar rainbowfish for a second tank once the first school has taught you the routine. Whichever type you choose, the colour you are buying only appears in a school of six or more in hard water — the numbers are in the rainbow fish care guide and on the water parameters page, and the adult sizes and lifespans are under rainbow fish size and lifespan.
Rainbow Fish Care FAQ
What is the most popular type of rainbow fish?
The boesemani rainbowfish (Melanotaenia boesemani), blue at the front and orange at the back, followed by the dwarf neon (M. praecox) and the turquoise or Lake Kutubu rainbowfish (M. lacustris).
Which rainbow fish is best for beginners?
Boesemani: hardy, 4 inches, colours up reliably in a school of six in a 40–55 gallon tank. The Australian rainbowfish and turquoise are equally tough; dwarf neons suit a 20-gallon long.
What is the smallest rainbow fish?
The threadfin rainbowfish (Iriatherina werneri) and Gertrude's spotted blue-eye at about 1.5 inches, then the forktail blue-eye and dwarf neon at 2–2.5 inches. All need a school of eight or more.
What is the biggest rainbow fish?
The red rainbowfish (Glossolepis incisus) at 5–6 inches, and the Australian splendid and parkinson's rainbowfish at 5 inches. They need 55–75 gallon tanks.
Can different types of rainbow fish live together?
Yes, in 55 gallons or more, as long as each species has its own school of six. Boesemani and turquoise, or dwarf neons and threadfins, are classic pairs. Melanotaenia species will hybridise if kept in mixed groups too small to school properly.
Which rainbow fish are the most colourful?
Boesemani (blue and orange), red rainbowfish (solid red males), turquoise (electric blue) and dwarf neon (violet with red fins). Colour depends on a school, hard water, a dark background and good food more than on the species.