Spotted Blue-eye

Pseudomugil gertrudae

Also sold as Spotted blue eye rainbowfish · Gertrude's blue-eye

Spotted Blue-eye (Pseudomugil gertrudae) is a peaceful freshwater fish that reaches about 3.8 cm (1.5 in) and swims in open water in a shoal. It wants 70–82°F (21–28°C) and pH 4.5–7.5, is kept in groups of 8 or more, and needs a tank of at least 41 L (11 gal).

At a glance

Type	Fish
Adult size	3.8 cm (1.5 in)
Minimum tank	41 L (11 gal)
Group size	8 or more
Temperature	70–82°F (21–28°C)
pH	4.5–7.5
Temperament	Peaceful
Lifespan	1–2 years
Eats shrimp	Shrimplets only

Before it goes in

Spotted Blue-eye needs at least 41 L (11 gal). The smallest size in this library that clears that is the 15 Gallon.
Keep 8 or more. Below that it hides, colours down and is far more likely to be picked on.
Adult shrimp are safe; shrimplets will be eaten, so a shrimp colony will not grow in the same tank.
It is the wrong size to share a tank with Goldfish, Angelfish and Axolotl: it ends up as food.
It holds at 70–82°F (21–28°C). That shares a window with Betta and Cherry Shrimp.
Sources say not to put it in a newly set-up tank — give the tank a few months first.
A group of 8 takes up roughly 63% of what a 15 Gallon will comfortably hold, so plan the rest of the stock around it.

What tank size does it need?

At least 41 L (11 gal). The smallest size here that clears it is the 15 Gallon.

How many should I keep?

8 or more. Fewer than that and it spends its time hiding instead of out in the open.

Will it eat shrimp?

Adults are safe, shrimplets are not. You can keep shrimp with it; you just will not get a growing colony.

What water does it want?

70–82°F (21–28°C), pH 4.5–7.5.

How long does it live?

1–2 years in a tank that suits it. That is how long you are signing up for.

Can it go in a new tank?

No. Sources say not to add it to a newly set-up tank — it wants a tank that has been running for months.

Good tank mates

Tank mates from this library that share its temperature window, are peaceful and eat neither it nor its young: Cherry Shrimp, Bristlenose Pleco, Celestial Pearl Danio, Molly and Otocinclus.
Plants that hold up with it: Hygrophila corymbosa 'Siamensis', Water Sprite, Anubias nana 'Petite' and Cryptocoryne wendtii.

Often compared with

	Spotted Blue-eye	Pacific Blue-eye	Forktail Rainbowfish
Adult size	3.8 cm	7 cm	5 cm
Min tank	41 L	54 L	50 L
Group	8+	8+	6+
Temperature	70–82°F (21–28°C)	68–79°F (20–26°C)	75–82°F (24–28°C)
Eats shrimp	Shrimplets only	Shrimplets only	Shrimplets only

More livestock

Plan a tank with Spotted Blue-eye →

Sources (4) · checked Sep 2026