Marbled helogenes

Helogenes marmoratus

Also known as Smoothhead catfish, Midnight cat

FreshwaterFish

Care at a glance

Temperature: 73–82°F (23–28°C)
pH: 4.5–6.8
Adult size: 3.1 in (8 cm)
Minimum tank: 14 gal (54 L)
Temperament: Peaceful
Social behavior: Social
Swim level: Middle
Difficulty: Medium
Breeding: No record
Rarity: Rare
Origin: Blackwater creeks of the Guianas and Amazon
Family: Cetopsidae

Overview

This is a shy, night-active catfish that does best in a small group of its own kind, so keep several together and they will feel secure enough to show themselves. By day they hang among leaf litter and roots, drifting out to feed once the lights go down. They are gentle and easily outcompeted, so choose small, peaceful blackwater tankmates and feed at lights-out with fine sinking and frozen foods such as bloodworm and daphnia so enough reaches them. A dimly lit tank of around 54 liters or more, heavy with cover, suits a group.

In the wild

The marbled helogenes lives in shaded blackwater and clearwater forest streams of the Guianas and Amazon, among drifting leaf litter and tangled roots. Recreate that with a soft, dark setup: dim light, tannin-stained water from botanicals and wood, and plenty of litter to hide in. It wants warm, very soft, acidic water, so aim for 23 to 28 C and a low pH of 4.5 to 6.8.

Good to know

Helogenes marmoratus is the hobby's cetopsid, or whale catfish, though it sits at the gentle end of a family that also includes flesh-eating relatives. It is a soft-bodied, leaf-patterned fish reaching about 8 centimeters. It has not been bred in aquaria, so its spawning habits are undocumented, but in the wild it feeds heavily on ants and other terrestrial insects that fall to the water.

Did you know

It often lies on its side among the leaf litter, colored like a dead leaf, and drifts slowly through the water at an angle rather than swimming upright. The disguise is so complete that keepers lose track of it in their own tanks.