Nijssen's Corydoras

Geographic Origin and Biotope: Endemic rarity of the Ucayali River basin, in central-eastern Peru. Resides in small forest streams characterized by dark or amber waters, thickly shaded by lush vegetation and covered by intricate root tangles.

Taxonomy and Morphology: Species discovered in honor of the ichthyologist Han Nijssen. Member of the "short-snouted" Callichthyidae. Reaches 5 cm (2 inches); its appearance is extremely round, compact, and graceful compared to other variants of the genus.

Social Behavior: Essence of tranquility. Strictly needs conspecific interaction: inserted in schools of over 8 individuals, it will confidently inspect the bends of the tank with rhythmic and harmless liveliness.

Coloration and Sexual Dimorphism: Distinguished by three huge dark "saddle" spots: a deep orbital mask, a majestic black block under the dorsal fin, and a third saddle along the caudal peduncle, on a pale cream background. Bellies of females visibly swollen if gravid.

Aquarium Setup: Requires dark setups, preferably "blackwater" biotopes: fine and non-reflective silica sand, thick leaf deposits (Catappa), and hut-like woody roots. Hates bright lights, mitigated with floating flora.

Diet and Feeding: Eminently predator of micro-zoobenthos. Often shuns classic flakes: feed regularly with sinking foods for bottom fish with a very high protein level, mixed with bloodworms, white worms, and live or frozen daphnia.

Water Quality: Optimal maintenance at 22-26°C (72-79°F). Recommended medium/soft hardnesses (GH 2-12). pH between 6.0 and 7.2. Suffers dramatically from the accumulation of putrefied bacterial debris in the substrate: frequent changes and light water siphonings are necessary.

Compatibility and Tankmates: The roommate par excellence for tiny South American rasboras (Nannostomus, Boraras) or small Apistogramma. Strictly eclipse the presence of intrusive territorial fish or any larger predator that could swallow it.

Aquarium Reproduction: Considerable challenge for the breeder: triggered by intense cold thermal shocks. Couples lay a few robust adhesive eggs individually on fine-leaved flora (Mosses). Marked tendency of the colony to devour its own brood.

Risks and Diseases: Irreparable and deadly loss of barbels if housed on rough inert quartz. It is ruthlessly sensitive to copper and does not tolerate shock treatments against classic mycoses. Avoid nocturnal oxygen drops.