Blue-spotted Rainbowfish
Pseudomugil gertrudae
The Blue-spotted Rainbowfish (Pseudomugil gertrudae) is a peaceful fish that's a good step up once you have a little experience. Give it a tank of at least 40 litres (11 US gallons), water held at 72-82°F, and a pH of 5.5-7.5. Always keep a group of at least 6 - they feel safest in numbers.
Captive lifespan reflects typical experience in a home aquarium, not maximum recorded age; genetics, sourcing, and care vary.
Natural distribution
Australia / New Guinea
- Australia & Oceania
Regional colours match the stocking calculator's origin map.
Blue-spotted Rainbowfish Tank Setup
Give them a tank of at least 40 litres (11 US gallons). As open-water swimmers they care more about swimming length than height, so a longer tank is ideal. Keep the water at 72-82°F with a pH around 5.5-7.5, 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 Blue-spotted Rainbowfish Eat?
They have small mouths, so stick to small foods: crushed flake, fine granules, and now and then a treat of frozen or live foods such as daphnia or baby brine shrimp. Anything too large simply gets ignored.
Blue-spotted Rainbowfish Tank Mates
Keep in groups of at least 6. Very small and delicate; avoid housing with boisterous or large tankmates. Best in a species or nano community setup. The Blue-spotted 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 Blue-spotted 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.
Blue-spotted Rainbowfish - frequently asked questions
What size tank do Blue-spotted Rainbowfish need?
Blue-spotted Rainbowfish need a tank of at least 40 litres (11 US gallons). A bigger tank is always easier to keep stable, and gives them more room to settle in and behave naturally.
How many Blue-spotted Rainbowfish should I keep together?
Keep a group of at least 6. Blue-spotted Rainbowfish are a shoaling species and become stressed, lose their colour, or hide when kept singly or in pairs.
What water parameters do Blue-spotted Rainbowfish need?
Keep them at 72-82°F with a pH of 5.5-7.5, 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 Blue-spotted Rainbowfish eat?
Blue-spotted Rainbowfish have small mouths, so they need small foods. Crushed flake and fine granules form the staple, with the occasional treat of frozen or live foods such as daphnia or baby brine shrimp. Feed small amounts once or twice a day, and remove anything they don't eat.
Are Blue-spotted Rainbowfish good for beginners?
Blue-spotted 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 Blue-spotted Rainbowfish
- Buying fewer than 6 - Blue-spotted Rainbowfishs need a proper school to feel secure; isolated individuals hide, fail to colour up, or become stressed.
Building a community? Run the full list through the stocking calculator before you add anything else.
Great tank mates
Chosen from temperament, overlapping temperature/pH bands, plausible minimum tank footprints, and size versus yours in App-aquatic data. Hobby nuance always wins - verify stocking and temperament before purchasing.
Fish to avoid mixing with Blue-spotted 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
