Dwarf medaka

Oryzias minutillus

Also known as Minute ricefish

FreshwaterFish

Care at a glance

Temperature: 72–79°F (22–26°C)
pH: 6.0–7.5
Adult size: 0.8 in (2 cm)
Minimum tank: 5 gal (20 L)
Temperament: Peaceful
Social behavior: Schooling
Swim level: Middle
Difficulty: Medium
Breeding: Medium
Rarity: Rare
Origin: Chao Phraya and Mekong lowlands, Thailand
Family: Adrianichthyidae

Overview

The dwarf medaka is one of the smallest fish in the hobby, a peaceful schooler barely two centimeters long that can live out a full life in a small planted tank. Keep it in a group of at least six, ideally a larger colony, where it feels secure and stays out in the open. It is community safe but so tiny that it really belongs in a species tank or with equally minute, gentle companions and no fish large enough to eat it. Feed small foods: crushed flake, powdered fry food, microworm, and baby brine shrimp. A gently filtered tank of around 20 liters with moss and fine plants houses a colony well.

In the wild

Oryzias minutillus comes from lowland Thailand, in the Chao Phraya and Mekong drainages, where it drifts in still and slow waters such as ditches, ponds, and rice paddies among dense plants. Recreate that with a heavily planted, gently filtered tank and calm water. It likes warm, soft to neutral conditions, about 22 to 26 C at roughly pH 6.0 to 7.5, and a quiet tank with little current lets this delicate fish feed and settle.

Good to know

Oryzias minutillus is a ricefish of the family Adrianichthyidae and the smallest of the medakas, with adults reaching only about 2 centimeters; its name means very small. As in other medakas the fertilized eggs ride at the female's vent before she attaches them to plants, and it will breed in a quiet planted tank, rated medium mainly because the tiny fry need very small first foods.

Did you know

A full-grown dwarf medaka is shorter than the width of an adult's fingernail. It is small enough that a mature, breeding colony can live comfortably in a jar-sized volume that would barely suit a single ordinary community fish.