Ancestor cory

Hoplisoma noxium

Also known as Corydoras noxium, CW004

FreshwaterFish

Ancestor cory (Hoplisoma noxium) — The Wet Spot Tropical Fish · Used with permission

Care at a glance

Temperature: 75–82°F (24–28°C)
pH: 5.5–7.0
Adult size: 2.4 in (6 cm)
Minimum tank: 16 gal (60 L)
Temperament: Peaceful
Social behavior: Shoaling
Swim level: Bottom
Difficulty: Medium
Breeding: No record
Rarity: Rare
Origin: Igarape do Buriti, Rio Tapajos basin near Jacareacanga, Para, Brazil
Family: Callichthyidae

Overview

Keep six or more over sand in 60 liters. It eats sinking granules, wafers, and frozen foods and behaves like a model peaceful shoaler. There is no published breeding report; the standard cool-water-change method is the obvious starting point for anyone lucky enough to hold a group. Imports remain scarce and sought after.

In the wild

The ancestor cory comes from a small forest stream in the Tapajos basin near Jacareacanga, Brazil, where it shoals over sand in warm, gently acidic water. Keep it on fine sand with wood shade and leaf litter at 24 to 28 degrees Celsius, pH 5.5 to 7.0, with the clean, oxygen-rich water Tapajos fish expect.

Good to know

Hobbyists knew this fish for years as CW004, the ancestor cory, before Tencatt, Ohara, Carvalho, Grant and Britto described it in 2025 as Hoplisoma noxium; under the catalog's trade-genus convention it files as Corydoras noxium. It reaches about 6 centimeters, and related color forms carry the codes CW155, CW156 and CW167.

Did you know

Its hobby name predates its scientific one: keepers called CW004 the ancestor cory because its heavy mask and arch look like the pattern other corys seem built from, and science only caught up in 2025.