小兵鲶 · Pygmy Cory

Overview

The tiny Gastrodermus pygmaeus differs from many cory-type catfishes by spending substantial time in midwater. It is peaceful but easily intimidated or eaten by larger companions, so group size and feeding access matter more than simply finding spare space near the bottom.

Distribution & habitat

It appears restricted to Brazil's Madeira basin. Small tributaries, creeks, pools, and flooded forest provide habitat, with groups sheltering around marginal vegetation and roots.

Aquarium setup

Use subdued lighting and plentiful cover. Dense planting, driftwood, roots, and optional surface vegetation suit it. Alternatively, sand, wood, and a maintained leaf layer can create a more open natural setting. Remove deteriorating leaf material before it accumulates. Clean substrate and deliberate feeding remain necessary despite the species' reputation as a scavenger.

Diet & feeding

Food must fit its tiny mouth. Choose fine dry foods or crush larger particles, and include small live or frozen items such as screened Daphnia and brine shrimp nauplii. Check that the group receives food directly rather than relying on leftovers.

Behaviour & compatibility

Keep at least six, preferably ten or more when space allows. A dedicated group or a community of similarly tiny, calm fishes is suitable. Larger cichlids, gouramis, and catfishes can present predation or feeding-competition problems. Allow for its midwater shoaling instead of treating it as a strictly bottom-dwelling resident.

Sexual dimorphism

Viewed from above, females are broader and rounder, especially when carrying eggs. They are usually slightly larger as well.

Breeding

General cory breeding methods can work, but the exceptionally small fry need finer initial food. Provide gentle sponge filtration and fine vegetation, with more males than females. Well-conditioned adults may respond to cooler water changes and increased oxygenation; repeated stimulation is not a guarantee of spawning.

Courtship involves pursuit and a T-shaped position. The female holds one egg between her pelvic fins before attaching it to glass or another surface. The precise fertilization pathway remains partly inferential. Adults eat eggs, so separate them or transfer eggs into matching, well-oxygenated water. Remove fungal eggs promptly.

Hatching takes about three to five days. Once the yolk is absorbed, offer infusoria-sized foods before progressing to microworms or brine shrimp nauplii. A thin sand layer may improve the condition of growing fry.

Notes

The continuous dark lateral stripe helps distinguish it from other miniature corys. Occasional surface gulps are normal auxiliary breathing; increased frequency warrants attention to water conditions. Stiff pectoral spines can catch in nets or puncture skin, requiring care during transfer.