Pseudacanthicus is a genus of large, heavily armored suckermouth catfish (family Loricariidae) from South American blackwater and clearwater rivers, recorded in the atlas from Brazil, Guyana, Suriname and French Guiana. Known in the hobby as cactus plecos for the dense covering of enlarged, spine-like odontodes across the body and fins, they are among the biggest and most predatory members of the pleco family — opportunistic omnivores that take meaty foods readily rather than grazing algae the way smaller loricariids do. The atlas covers 9 species, and the size range is substantial: roughly 9–35.5 in.
Cactus plecos rank among the most sought-after and expensive plecos in the hobby, prized for bold color forms — Pseudacanthicus pirarara (scarlet cactus pleco) and P. leopardus (leopard cactus pleco) are especially well known — but their adult size and territorial temperament mean they need large, well-filtered tanks and careful stocking with other big, robust fish. Two species in the genus carry CARES conservation priority in the atlas, flagging them as candidates for hobby breeding programs even though the broader IUCN picture recorded here is comparatively reassuring: four Least Concern species against one Data Deficient and three Not Evaluated, meaning several Pseudacanthicus have simply not been formally assessed yet.