Acestridium dichromum

Acestridium dichromum is one of the most extraordinary loricariids available to aquarists — a pencil-thin, almost cylindrical catfish with a strikingly bi-coloured body, the anterior half predominantly black and the posterior half white to pale, creating a dramatic two-tone appearance unique in the family. The genus Acestridium is a small group of highly specialised wood-associated loricariids from Amazonian blackwater systems.

In its natural habitat, A. dichromum is a strict xylophage — a wood-feeder — that spends its entire life on submerged logs and branches in blackwater streams and rivers of Brazil. The highly acidic, tannin-rich, mineralless water of these environments is among the most extreme in freshwater biology. The species does not graze hard surfaces as Otocinclus does but rather consumes the organic biofilm and microbial communities colonising waterlogged wood, and possibly small amounts of the wood itself.

Keeping Acestridium dichromum in the aquarium is a challenge suited only to experienced blackwater specialists. It requires extremely soft, very acidic water, abundant driftwood, dim lighting, and a complete absence of fish that might compete aggressively for its specialised food sources. The dramatic patterning and highly unusual biology of this species make it one of the most coveted loricariids among dedicated catfish collectors.

Water: Extremely soft, acidic water at pH 4.5–6.5 and 23–28°C; essentially mineralless (GH 0–3, KH 0–2); large weekly water changes with RO or soft rain-equivalent water. Tank: 60 litres minimum with abundant driftwood as the primary decor; blackwater with peat or catappa leaves; very dim lighting. Feeding: Relies on biofilm from aged driftwood; supplement with wood-boring catfish foods, algae wafers soaked in blackwater, and occasional meaty sinking foods. Breeding: Not documented in captivity. Compatibility: Keep only with other blackwater specialists tolerating very acidic, mineralless conditions.