Carinotetraodon borneensis

Overview

An uncommon small red-eyed freshwater puffer, Carinotetraodon borneensis sometimes arrives mixed with a similar species. Its loose social tendencies do not eliminate male territorial behavior. Keeping several requires ample space and extensive cover.

Distribution & habitat

Confirmed records are limited to southern Sarawak, Malaysian Borneo, in the Sarawak, Sadong, and Rajang systems. Slow margins with submerged terrestrial plants or aquatic vegetation are its likely habitat, rather than a firmly established preference.

Aquarium setup

Create a heavily structured aquarium with roots, branches, aquatic plants, and floating shade. Dried leaves add cover and support microbial growth. Keep filter outflow gentle. Frequent small water changes help prevent the deterioration to which this puffer is sensitive.

Diet & feeding

Puffer mouthparts grow continuously, so regularly provide manageable shelled foods such as snails, shellfish, or small crab legs to encourage wear. Add chopped shellfish, small earthworms, bloodworms, or Artemia. Dry preparations should not dominate feeding.

Attached growth may contribute to the natural diet, making biofilm on decor useful to retain. It should not be treated as a complete food supply.

Behaviour & compatibility

Although less aggressive than some relatives, it is most straightforward to keep alone. Peaceful shoaling cyprinids are a possible alternative only when too large to be prey but not large or assertive enough to threaten the puffer. Groups need generous shelter and room, with attention to disputes involving males.

Sexual dimorphism

Male gray mottling fades gradually into the pale underside. A narrow yellowish flank line, pale chevrons above, and a broad red belly stripe help distinguish males, whose tail often has dark and white edging. Females have a broader, sometimes broken pale side stripe, irregular light patches, and an unmarked whitish belly. Their yellowish tail carries reticulation and dark bars. Both sexes generally have red eyes, although some males appear blue-green.

Breeding

Breeding is unrecorded for this species. Egg scattering among plants and male guarding occur in a relative, but are not established here.

Notes

A similar red-eyed relative has conspicuous dark bars on both head and body in each sex. This species lacks that clear barred combination, so red eyes alone are insufficient for identification.