Pseudomugil Gertrudae
Pseudomugil gertrudae
The spotted blue-eye, a sparkling nano rainbowfish for soft, warm tanks.
| Difficulty | Intermediate |
| Min. Tank Size | 40 L |
| Temperature | 24.0–30.0 °C |
| pH Range | 5.5–7.5 |
| Max Size | 4.0 cm |
| Lifespan | 2-3 years |
| Diet | Omnivore |
| Temperament | Peaceful |
Overview
The Pseudomugil Gertrudae (Pseudomugil gertrudae) is the spotted blue-eye, a sparkling nano rainbowfish for soft, warm tanks. It is a popular choice among Australian aquarists, reaching around 4 cm and living roughly 2-3 years when properly cared for.
This complete guide covers how to keep the Pseudomugil Gertrudae successfully - tank size and setup, water parameters, the best foods (including recommended brands), suitable tank mates, breeding, sexing and the health issues to watch for. It is rated Intermediate to care for.
Natural Habitat & Origin
Rainbowfish come from the clear streams, lakes and billabongs of Australia and New Guinea. Males develop their most intense colour as they compete, especially in a sunny, well-planted tank with open swimming space.
Matching the temperature, water chemistry and cover a species evolved with is the simplest route to keeping it healthy and seeing its natural behaviour and colour.
Tank Size & Aquarium Setup
Provide a minimum of 40 litres for the Pseudomugil Gertrudae. As a group-living species, swimming length and floor space matter more than height.
Live plants, driftwood and shaded retreats give security and show off the fish's colours against a natural backdrop.
Always add fish only to a fully cycled, mature tank with stable biological filtration. Provide strong, well-oxygenated flow for this active, oxygen-hungry species.
Water Parameters
Keep the Pseudomugil Gertrudae in stable water at 24-30 °C with a pH of 5.5-7.5. It adapts to a moderate range, so stability matters more than an exact figure.
Test regularly: ammonia and nitrite must read zero, and nitrate should be kept low with routine partial water changes. Always dechlorinate and temperature-match new water, because sudden swings cause far more illness than water that is stable but slightly imperfect.
Diet & Feeding
The Pseudomugil Gertrudae is an easy-going omnivore that accepts a wide range of foods.
In Australia, good options include API Tropical Flakes or Pellets, Hikari Micro Pellets or Tropical, and Dymax frozen brine shrimp and bloodworm as treats. Feed small amounts once or twice a day (only what is cleared in a minute or two), vary the diet for the best colour and health, and avoid overfeeding, which is the leading cause of poor water quality.
Temperament & Tank Mates
The Pseudomugil Gertrudae is peaceful and community-friendly. It mixes well with other calm species that share its temperature (24-30 °C) and pH (5.5-7.5) needs, are too large to be eaten and not large enough to eat it.
Crucially, keep the Pseudomugil Gertrudae in a group of at least 6 (8 or more is better). A proper shoal is calmer, bolder, more colourful and far less likely to harass tank mates - keeping too few is a common cause of stress and nipping.
Breeding
The Pseudomugil Gertrudae is an egg-scattering species. To breed it, condition a group on rich foods, then move them to a dim tank with fine-leaved plants or a spawning mop; the parents scatter eggs and will eat them, so remove the adults after spawning.
Even if you are not planning to breed it, recognising this behaviour helps you understand what you are seeing and respond well - for example by adding cover for fry or giving a guarding pair extra space.
How to Tell Males from Females
Males are larger, deeper-bodied and far more colourful, with taller fins, while females are slimmer and plainer.
Common Health Problems
Like most aquarium species it can suffer from white spot (ich), fin rot and fungal or bacterial infections, almost always triggered by stress or poor water quality. Quarantine new arrivals for 2-4 weeks and watch daily for early signs such as loss of appetite, unusual hiding, clamped fins or laboured breathing - caught early, most issues are very treatable.
Prevention beats cure: keep water pristine, avoid overstocking and overfeeding, quarantine new arrivals, and act at the first sign of trouble.
Is the Pseudomugil Gertrudae Right for You?
The Pseudomugil Gertrudae suits keepers with some experience and a stable, mature, appropriately sized tank, as long as you can provide at least 40 litres, water at 24-30 °C and pH 5.5-7.5, the right diet and a proper group of its own kind.
Meet those needs and the Pseudomugil Gertrudae will reward you for around 2-3 years. Use our free aquarium calculators to plan your setup, and explore our other fish, plant and disease guides to build a thriving aquarium.
