Cruciatus Loach

Yunnanilus cruciatus is a small, lively nemacheilid loach from the rivers and streams of Yunnan province in southwestern China. Its common and scientific name reference the distinctive cross-shaped (cruciform) dorsal marking visible in well-conditioned individuals — a dark saddle-mark intersected by a lateral stripe, creating a distinctive X or cross pattern. The species is relatively small and active, darting energetically through the water column in groups.

In the aquarium, Y. cruciatus requires the cool, well-oxygenated conditions typical of upland Chinese stream fish. It is somewhat more water-column active than strict hillstream loaches and appreciates open swimming areas alongside rocky shelter. Its small size makes it suitable for 60-litre tanks when kept in groups of six or more, making it accessible to keepers with limited space who wish to keep hillstream-adapted fish.

This species is more tolerant of moderate current than extreme-flow hillstream loaches and can be maintained in a standard cool-water aquarium with good filtration and surface agitation rather than requiring a dedicated hillstream powerhead setup. However, water temperature must remain firmly in the cool range — above 22 °C will cause chronic stress.

Water: 16–22°C, pH 6.5–7.5, GH 4–15, KH 2–8; moderate flow and good surface agitation; cool water is essential and non-negotiable for long-term health. Tank: 60 L minimum; mix of open swimming areas and rocky hiding zones; fine gravel or smooth pebble substrate; no need for extreme powerhead flow. Feeding: Omnivore — small sinking pellets, frozen daphnia and cyclops, microworms; small mouth size requires appropriately sized food items. Breeding: Rarely documented in captivity; condition with cool water changes; eggs likely scattered over fine gravel; fry require infusoria and microfauna. Compatibility: Peaceful; good company for other cool-water species including White Cloud Mountain Minnows, hillstream loaches, and small danios.