Axelrod's Rainbowfish (Melanotaenia herbertaxelrodi) in a freshwater aquarium
Intermediate carePeacefulSchool of 6+Papua New Guinea

Axelrod's Rainbowfish

Melanotaenia herbertaxelrodi

The Axelrod's Rainbowfish (Melanotaenia herbertaxelrodi) is a peaceful fish that's a good step up once you have a little experience. Give it a tank of at least 150 litres (40 US gallons), water held at 75-82°F, and a pH of 6.5-8. Always keep a group of at least 6 - they feel safest in numbers.

Care levelIntermediate
TemperamentPeaceful
Min tank size40 US gal
pH range6.5-8
Temperature75-82°F
Max size3.9 in (10.0 cm)
Captive lifespan5-10 years
SchoolingYes · 6+ recommended
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Captive lifespan reflects typical experience in a home aquarium, not maximum recorded age; genetics, sourcing, and care vary.

Natural distribution

Papua New Guinea

  • Australia & Oceania

Regional colours match the stocking calculator's origin map.

Axelrod's Rainbowfish Tank Setup

Give them a tank of at least 150 litres (40 US gallons). As open-water swimmers they care more about swimming length than height, so a longer tank is ideal. Keep the water at 75-82°F with a pH around 6.5-8, and avoid sudden swings. Always keep a group of at least 6 of their own kind - kept alone or in pairs they tend to turn shy, nippy, or wash out in colour.

What Do Axelrod's Rainbowfish Eat?

They're not fussy eaters - feed a varied diet, rotating good-quality dry, frozen, and gel foods rather than the same thing every day, and match the food size to their mouths.

Axelrod's Rainbowfish Tank Mates

Active swimmer; keep in groups for best display The Axelrod's Rainbowfish is peaceful, which is the first thing to weigh up when you choose tank mates. It's a shoaling fish, so settle a group of 6 or more of its own kind before adding anything else - a stressed, lonely fish is far more likely to nip or hide. Before you buy, run your full stocking list through our stocking calculator. It weighs temperament, adult size, and water needs together, which a single species page can't do on its own.

Are Axelrod's Rainbowfish Good for Beginners?

Doable once you test water regularly and catch problems before fish look sick. If this is your first tank, pick something more forgiving and come back later.

Axelrod's Rainbowfish - frequently asked questions

What size tank do Axelrod's Rainbowfish need?

Axelrod's Rainbowfish need a tank of at least 150 litres (40 US gallons). A bigger tank is always easier to keep stable, and gives them more room to settle in and behave naturally.

How many Axelrod's Rainbowfish should I keep together?

Keep a group of at least 6. Axelrod's Rainbowfish are a shoaling species and become stressed, lose their colour, or hide when kept singly or in pairs.

What water parameters do Axelrod's Rainbowfish need?

Keep them at 75-82°F with a pH of 6.5-8, steady rather than chased to an exact figure. In a cycled tank, ammonia and nitrite should both read 0 ppm, with nitrate kept low through regular water changes.

What do Axelrod's Rainbowfish eat?

Axelrod's Rainbowfish are omnivores and aren't fussy eaters. Feed a varied mix of good-quality dry, frozen, and gel foods, and match the food size to their mouths. Feed small amounts once or twice a day, and remove anything they don't eat.

Are Axelrod's Rainbowfish good for beginners?

Axelrod's Rainbowfish are best for keepers with a little experience. They are manageable once you test water regularly and catch problems early; a complete beginner may prefer something more forgiving first.

Common mistakes with Axelrod's Rainbowfish

  • Buying fewer than 6 - Axelrod's Rainbowfishs need a proper school to feel secure; isolated individuals hide, fail to colour up, or become stressed.
  • Underestimating tank size - the minimum footprint is 150 litres (40 US gallons); impulse buying into a smaller tank leads to stress and shortened lifespan.

Building a community? Run the full list through the stocking calculator before you add anything else.

Fish to avoid mixing with Axelrod's Rainbowfish

These well-known species are commonly sold alongside this fish but are not recommended tank mates - verify before purchasing.

  • OscarPredator - Oscar will eat or injure smaller tank mates
  • Pea PufferPredator - Pea Puffer will eat or injure smaller tank mates
  • Betta (Male)Predator - Betta (Male) will eat or injure smaller tank mates