The spotted blue eye is a tiny rainbowfish with bright blue eyes, yellow fins and lively displays, which makes it ideal for a planted nano or small community tank. It is easy to keep once you give it a proper group, soft to medium water and small, varied food.
This guide covers the tank size and water conditions spotted blue eyes need, how to set up the aquarium, which tank mates work, what to feed and what to expect if they spawn. It is about the spotted blue-eye (Pseudomugil gertrudae), sometimes sold as Gertrude’s blue eye.
Key Takeaways
- Spotted blue eyes grow to only about 3 to 4 cm, so a planted tank of 45 litres or more suits a group.
- Keep at least eight, with more females than males, so displays stay friendly.
- Aim for 24 to 28°C, a pH of about 6.0 to 7.5 and soft to medium water with gentle flow.
- Feed small foods such as crushed flake, micro pellets, baby brine shrimp and daphnia once or twice a day.
- Choose tiny, peaceful tank mates and plan for a short lifespan of around one to two years.
What Do Spotted Blue Eyes Need in an Aquarium?
Spotted blue eyes come from slow, heavily vegetated streams and swamps in northern Australia and New Guinea. They spend most of their time in the upper half of the tank, darting between plants. Calm water, plenty of greenery and stable conditions bring out their best colour and display behaviour.
Tank size and water conditions
A group of eight needs a tank of at least 45 litres, ideally 60 cm long. They prefer soft to medium water and are sensitive to sudden changes, so keep conditions steady and change 20 to 25 per cent of the water each week with dechlorinated water at the same temperature.
| Parameter | Target for spotted blue eyes |
|---|---|
| Tank size | 45 litres or more for a group |
| Temperature | 24 to 28°C |
| pH | About 6.0 to 7.5 |
| Hardness | Soft to medium |
| Adult size | About 3 to 4 cm |
| Lifespan | Around 1 to 2 years |
How many spotted blue eyes should you keep?
These are shoaling fish, so keep at least eight. Males spar and display to each other, which is part of their charm, but too many males in a small group can lead to stress. Two or three females for every male keeps things calm.
How to Set Up a Spotted Blue Eye Tank
Plan the tank around plants and gentle flow.
Plants and cover
Use plenty of fine-leaved plants, mosses and floating plants, leaving open water near the surface for swimming. Dense planting gives females somewhere to escape persistent males and provides surfaces for spawning.
Filter, lid and lighting
A sponge filter or a small filter with a spray bar keeps flow gentle. Fit a tight lid, as these small, active fish can jump. Moderate light filtered through floating plants shows off their blue eyes and yellow fins.
Tank Mates for Spotted Blue Eyes
Spotted blue eyes are peaceful but very small, so tank mates must be just as small and gentle.
| Tank mate | Suitable? | Notes |
|---|---|---|
| Chilli and other micro rasboras | Yes | Similar size and temperament |
| Ember tetras | Yes | Peaceful and share soft water |
| Pygmy corydoras | Yes | Stay low and leave them alone |
| Cherry and other dwarf shrimp | Yes | Adults are safe; some shrimplets may be eaten |
| Larger barbs and boisterous fish | No | Outcompete them for food and stress them |
| Angelfish and cichlids | No | Will eat fish this small |
A simple rule: if a fish is peaceful and fully grown at under about 4 cm, it is likely to suit a spotted blue eye tank.
What to Feed Spotted Blue Eyes
Their mouths are tiny, so food must be small. Offer crushed quality flake or micro pellets as a staple, with baby brine shrimp, daphnia and cyclops several times a week for colour and condition.
Feed small amounts once or twice a day, giving only what they eat in a minute or two. They feed mostly at the surface and in mid-water, so slow-sinking foods work best.
How to tell they are eating well
Well-fed spotted blue eyes have slightly rounded bellies, bright colour and males that display often. Pale colour or thin bellies usually mean the food is too large or faster tank mates are taking it first.
Breeding Spotted Blue Eyes
In a well-planted tank, spotted blue eyes often spawn on their own. Females scatter a few eggs a day among moss, fine-leaved plants or a spawning mop over several weeks. Adults will eat eggs and fry, so move the plants or mop to a separate container to raise the young.
The eggs usually hatch within one to three weeks depending on temperature. Feed the fry infusoria or liquid fry food at first, then baby brine shrimp once they can take it. Because the adults are short-lived, regular breeding is the best way to keep a group going.
Give Your Spotted Blue Eyes a Settled Home
With a proper group, plenty of plants, stable soft to medium water and small, varied food, spotted blue eyes are one of the most rewarding nano fish you can keep. Choose tiny, peaceful tank mates and enjoy their displays.
For more on killifish and rainbowfish, read our guide to neon dwarf rainbowfish care and our guide to gardneri killifish care, or browse killifish for sale.
Frequently Asked Questions
How big do spotted blue eye rainbowfish get?
They are tiny, usually reaching about 3 to 4 cm, which makes them a good choice for planted nano tanks.
How many spotted blue eyes should be kept together?
Keep at least eight, with two or three females for every male, so the males’ displays do not become stressful.
What size tank do spotted blue eyes need?
A group needs a planted tank of at least 45 litres, ideally 60 cm long, with gentle flow and a tight lid.
Can spotted blue eyes live with shrimp?
Yes. They are peaceful and leave adult shrimp alone, although they may eat some very small shrimplets.
What do spotted blue eyes eat?
Feed small foods such as crushed flake, micro pellets, baby brine shrimp, daphnia and cyclops.
How long do spotted blue eyes live?
They are short-lived, usually around one to two years, so many keepers let them breed to keep the group going.
What temperature do spotted blue eyes need?
Keep them at 24 to 28°C with a reliable heater and avoid sudden changes in temperature.