甲刺鱼 · Armoured Stickleback

Overview

Indostomus paradoxus is a minute fish whose weak competitive feeding makes a busy general community unsuitable. A quiet, densely structured aquarium, tiny live prey, and opportunities for interaction with its own kind are central to care. Identification also deserves attention because similar species may be sold under its name.

Distribution & habitat

Native to Myanmar, it was first described from northern Lake Indawgyi. Later records include Ayeyarwady tributaries around Myitkyina and localities farther south in the delta, extending its known range beyond the northern lake region.

Members of the genus favor still or sluggish water among submerged plants, bankside vegetation, and leaf litter. This species' original locality contained black clay, algae, and decaying vegetation, whereas a southern collection came from a clear, muddy pond with dense aquatic plants. Its habitat should not be reduced to a single water appearance.

Aquarium setup

Use abundant planting over a soft bottom; fine gravel is also acceptable. Roots, branches, floating plants, and leaves add sheltered surfaces while softening the light. Suitably narrow plastic tubes provide both retreats and potential spawning chambers.

Keep filtration gentle rather than exposing the fish to strong currents. A mature planted system also supports microscopic animals that can supplement feeding.

Diet & feeding

Its principal prey consists of tiny crustaceans, worms, insect larvae, and other zooplankton. Be prepared to supply appropriately small live foods, including newly hatched brine shrimp, Daphnia, and microworms. Acceptance of dry or frozen food should not be assumed.

Grindal worms are usually rejected despite their apparently suitable size. Resident microfauna may help, but observing intake and maintaining an external food supply remain necessary.

Behaviour & compatibility

Larger fishes can eat it, and faster competitors readily outcompete it for food. A species aquarium is preferable, although equally small, quiet companions may work. It does not form a conventional shoal, yet conspecific interaction appears beneficial; at least four to six individuals allow a wider range of behavior.

Males defend small territories and challenge rivals without normally injuring them. Provide enough structure and small retreats for multiple fish.

Sexual dimorphism

Adult males develop broad, elongated pelvic fins with inward-curving outer rays. Female pelvic fins are narrower and straighter, and females carrying eggs become fuller through the abdomen.

Breeding

Aquarium spawning has been achieved repeatedly. A male selects a narrow crevice, cave, bamboo section, or plastic tube and guards its immediate surroundings. Breeding males become paler and reddish, with light brown dorsal and anal fin stripes. Fin displays and tail-region quivering at the entrance attract females; receptive females become conspicuously pale and show a prominent genital papilla.

The pair commonly turns upside down to attach eggs overhead. Spawning may occur in several bouts separated by brief female departures, producing about 5–40 eggs. The female then leaves, while the male tends the brood alone, departing briefly to feed. Guarding continues until the young swim freely and disperse.

Some fry may survive in mature, predator-free aquariums. Alternatively, visible fry can be siphoned into separate accommodation, although their minute size makes this difficult. Rotifers, Paramecium, or comparable microscopic food are needed initially.

Notes

Unlike adult males of close relatives, this species lacks dark dorsal and anal fin bands; breeding males show pale brown ones. A pale brown underside and white throat with occasional brown spots are additional clues.

The similar Indostomus crocodilus is readily confused with it in the trade. Indostomus spinosus has a darker underside, more throat spots, and more strongly serrated head ridges. A sales label alone is insufficient identification.