Not furry, but we like them anyway.
Spotted Blue-eye
Pseudomugil gertrudae Weber, 1911
Also called Gertrude's blue-eye, Delicate blue-eye, Northern blue-eye
From Northern Australia (Northern Territory and Cape York Peninsula, Queensland), southern New Guinea and the Aru Islands of eastern Indonesia.123
At a glance the quick version
Wikipedia: usually 2.5 cm, rarely 3 cm; FishBase and Seriously Fish: up to 3.8 cm SL
Looks how to spot one
Scaled, tiny translucent blue-eye
A tiny, see-through to silvery-white fish, sometimes tinted tan or yellow. The back half carries thin black lines that break into spots, and the yellow fins are speckled with black spots, a feature that sets it apart from its relatives. Males are showier with longer fins.31
Personality what they are like
Peaceful but quite shy, so it is happiest with other small, gentle fish and dwarf shrimp rather than in a busy community.1
Daily activity how busy a day looks
A small shoaling fish that stays near plants in calm, shallow water.13
Grooming and care the hands-on bits
Can live in a small, well-planted aquarium; keep conditions stable and offer plenty of tiny live food.31
Home where they are happiest
Minimum tank base about 45 x 30 cm (around 41 litres). Temperature 21-28 °C, soft to medium water, pH 4.5-7.5 (FishBase gives 6.0-6.7), hardness 5-12 dGH. Dense plants, wood and leaf litter suit it.12
Food basics what goes in the bowl
Eats algae and tiny invertebrates in nature. In the aquarium offer mostly small live foods such as Daphnia, Moina, baby brine shrimp and microworms.31
Company who they like around
Keep at least 8-10, ideally more.1
The story where it all began
Max Weber described it in 1911 from fish collected on Trangan Island in the Aru Islands. He named it after Gertrude Merton, wife of the German zoologist Hugo Merton, who visited the islands in 1907-08.32
Fun facts for the dinner table
- 1
It is named after Gertrude Merton, wife of zoologist Hugo Merton.3
- 2
Wild populations live in water ranging from very acidic to alkaline, with pH readings from about 3.7 to 9.4.3
- 3
Local forms differ: Aru Islands fish grow larger and some Australian forms have orange fins or bodies.3
- 4
Spotted fins are the feature that distinguishes it from other blue-eyes.1
Recognised by the official bits
- IUCN Red List
- Least Concern (assessed February 2019)2
- Taxonomy
- Family Pseudomugilidae; described by Weber in 19112
The care rhythm Furry Diary remembers it for you
A typical home-care rhythm for a Spotted Blue-eye. It is our own starting plan, not a vet's advice, and you can change every line in the app.
- FeedingSmall amounts once or twice a dayevery day
- Temperature checkevery day
- Water changeAbout 25% of the waterevery week
- Water testevery week
- Glass cleanevery week
- Filter rinseRinse in old tank water, never tap waterevery month
Owner questions the things everyone asks
How often should I feed my Spotted Blue-eye?
Feed your Spotted Blue-eye small amounts once or twice a day, as Furry Diary's starting plan suggests. This matches their natural grazing habit and keeps water quality stable. Furry Diary plan
What does a Spotted Blue-eye eat, and what should it never eat?
In the wild they eat algae and tiny invertebrates; in the aquarium offer small live foods like Daphnia, Moina, baby brine shrimp and microworms. What they should never eat varies by individual, so ask a good breeder or exotic-pet vet for guidance on safe commercial foods.31
How much space does a Spotted Blue-eye need?
A minimum tank base of about 45 x 30 cm (around 41 litres) is recommended for a small shoal. This gives them room to swim near plants in calm, shallow water.12
What temperature, light or water does a Spotted Blue-eye need?
Keep the water at 21, 28 °C, soft to medium, with pH 4.5, 7.5 (ideally 6.0, 6.7) and hardness 5, 12 dGH. Light needs vary; dense plants, wood and leaf litter create a natural shady environment.12
How often should I clean a Spotted Blue-eye's home?
Furry Diary's starting plan suggests a 25% water change and glass cleaning every 7 days, plus a filter rinse in old tank water (never tap) every 30 days. Regular testing keeps conditions stable. Furry Diary plan
Can a Spotted Blue-eye live with others?
Yes, they are peaceful but shy, so keep them in a group of at least 8, 10 (ideally more) with other small, gentle fish and dwarf shrimp. Avoid busy community tanks.1
How long does a Spotted Blue-eye live?
Lifespan varies with care and conditions; ask a good breeder or exotic-pet vet for typical expectations. With stable water and proper feeding they can thrive for a good while.
Can I handle a Spotted Blue-eye?
Handling is not recommended for this tiny, delicate fish; it causes stress and can damage their scales. Always use a soft net if you must move them, and ask a vet for best practices.
Written from the sources on this page, a few checked guides (VCA, ASPCA, RSPCA) and Furry Diary's own starting care plan. A friendly guide, not a vet's advice.
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Where this comes from
Every breed page shows where each fact comes from. If we got something wrong, sorry, we are pet people, not a science magazine. Tell us at support@furrydiary.app and we will fix it.
- Seriously Fish: Pseudomugil gertrudae (Spotted Blue-eye) seriouslyfish.comused for habitat, tank size, water parameters, diet, behaviour, group size, dimorphism
- FishBase: Pseudomugil gertrudae, Spotted blue-eye fishbase.seused for distribution, max length, water ranges, IUCN status, etymology
- Wikipedia: Spotted blue-eye en.wikipedia.orgused for other names, history, colour description, size, habitat pH, local forms
- VCA Animal Hospitals: Feeding times and frequency for your dog vcahospitals.comused for owner questions
- ASPCA: Dog grooming tips aspca.orgused for owner questions
- ASPCA: Cat grooming tips aspca.orgused for owner questions
- ASPCA: People foods to avoid feeding your pets aspca.orgused for owner questions
- RSPCA: What to feed your rabbit rspca.org.ukused for owner questions
Checked 2026-09-30. Text is written in our own words from these sources.