Spotted blue-eye

Where they come from (and why that matters)

Spotted blue-eyes (Pseudomugil gertrudae) come from northern Australia and southern New Guinea—think warm, shallow creeks, swampy margins, and weedy backwaters with gentle flow. That’s why they look so at home in a planted tank with calm water and lots of little “edges” to hang around.

Setting up their tank

You don’t need anything fancy, but you do want the vibe right: plants, gentle filtration, and a group big enough that they feel bold. In a bare tank they’ll look washed out and skittish. In a planted one, the males fire up and you’ll actually see the fun behavior people buy them for.

• Tank size: 10 gallons works, 15–20 gallons is even nicer for a proper group
• Group size: 8–12+ (they’re way better in numbers)
• Temp: mid-70s°F is a sweet spot (roughly 24–26°C)
• pH/hardness: they’re pretty forgiving as long as it’s stable; slightly acidic to neutral is easy mode
• Flow: gentle—think “plants barely moving,” not a river

Plant it like you mean it. I’ve had the best luck with fine-leaf stuff (Java moss, guppy grass, hornwort) plus some floating plants to dim the lights a bit. Dark substrate helps their spots and fins pop, too.

What to feed them

They’ve got small mouths and they love small foods. If you only feed big flakes, you’ll watch them “try” and then give up. Give them tiny stuff and you’ll see better color and more breeding behavior.

• Staples: crushed quality flake, micro pellets, and small granules
• Favorites: baby brine shrimp, daphnia, cyclops, and microworms
• Nice extras: frozen baby brine, frozen daphnia, finely chopped frozen foods

Behavior and tankmates

Spotted blue-eyes are peaceful, curious, and constantly “busy.” Males display at each other—fins up, little zig-zag dances—but it’s mostly show. The real key is keeping them with fish that won’t intimidate them or outcompete them at feeding time.

• Great tankmates: small rasboras, ember tetras, small peaceful danios, Corydoras (dwarfs are perfect), Otocinclus, shrimp (adults usually fine)
• Use caution: bigger tetras, boisterous barbs, and anything nippy
• Avoid: aggressive fish, fast piggy eaters, and anything that sees tiny fish as snacks

Breeding tips (fun and very doable)

These are one of those fish that will spawn in a community tank and you’ll never notice… until you spot a random tiny fry in the moss. They’re egg scatterers and they love fine-leaved plants and spawning mops.

• Give them a spawning target: Java moss clumps, guppy grass, or a yarn spawning mop
• Condition with live/frozen foods for a week or two (baby brine + daphnia is magic)
• If you want fry: move the mop/moss to a small rearing container or breeder tank every few days
• Fry foods: infusoria/green water at first, then microworms and baby brine shrimp as soon as they can take it

Common problems to watch for

Most issues I’ve seen with these come from the tank being too bare, too bright, or too chaotic. They’re hardy for their size, but they don’t love swings and they don’t compete well if bigger fish are hogging food.

• Shyness and dull color: usually not enough cover, too small a group, or lighting that’s too harsh
• Skinny fish: food pieces too big or tankmates out-eating them (watch during feeding)
• Fin damage: nippy tankmates or males crowded without enough visual breaks (plants help a lot)
• Sudden losses: new tank instability, temperature swings, or poor acclimation
• White spot/ich after stress: can pop up if they’re shipped and then tossed into a bright, busy tank