Spotted blue-eye
Pseudomugil gertrudae
intermediate careOverview
The spotted blue-eye (Pseudomugil gertrudae) is a dainty nano rainbowfish from the soft, tannin-stained waters of northern Australia and southern New Guinea. Barely 3.5 cm long, males sport spotted, feathered fins and glowing electric-blue eyes, which they flare constantly as they display to each other. Active, peaceful and endlessly charming in a shoal, it is a gorgeous fish for a mature planted nano — as long as you accept its naturally short life.
Tank & water
A shoal thrives in a mature, planted 38-litre (10-gallon) tank or larger with open swimming space.
- Temperature: 23–28 °C from a small heater.
- Water: soft, slightly acidic to neutral, pH 5.5–7.0; a little tannin from leaf litter suits them. Test with a kit.
- Densely planted with open water: fine plants and floating cover frame the open areas where males display.
- Gentle flow: a soft sponge filter keeps water clean without a strong current.
Feeding
Spotted blue-eyes are surface-and-midwater micropredators with small mouths. Offer fine crushed micro-pellets and powdered foods, supplemented generously with small live and frozen fare — baby brine shrimp, daphnia, cyclops and microworm. Feed small amounts several times a day; they feed near the top, so use floating and slow-sinking foods.
Behaviour & tankmates
Peaceful and lively, they suit a calm nano community. Good tankmates are other small, gentle fish and dwarf shrimp — small rasboras, celestial pearl danios and cherry shrimp. Avoid boisterous or fin-nipping fish. Keep a good shoal with several males so their fin-flaring displays are on show, and they will breed readily in a planted tank.
A slightly higher proportion of males keeps the constant fin-flaring on display, while dense fine-leaved plants and moss give any eggs and fry somewhere to hide. Because the fish are so small and short-lived, letting the shoal breed is the natural way to enjoy them over several years.
Give the spotted blue-eye a mature, soft-water planted nano and a full shoal, and its dotted fins and electric-blue eyes make it one of the liveliest little rainbowfish for a small tank — see our best nano aquarium picks.
Spotted blue-eye — frequently asked questions
Why do spotted blue-eyes have such a short lifespan?
Pseudomugil are naturally short-lived, small rainbowfish — one to two years is normal even with excellent care. They mature and breed quickly to make up for it, so keepers often maintain the species by letting a shoal spawn in a planted tank rather than expecting individual fish to live for years.
What water do spotted blue-eyes need?
Soft, slightly acidic to neutral, warm and stable — around pH 5.5–7.0. They come from soft, often tannin-stained pools and streams in northern Australia and New Guinea, so a mature planted tank with gentle flow and some botanicals suits them well.
Do male spotted blue-eyes really display?
Yes, and it is the highlight of the species. In a group with several males, they constantly flare their finnage and spar for the females' attention, showing off dotted fins and glowing blue eyes. A shoal with a good ratio of males keeps this display going throughout the day.
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