Dorsal spines (total): 1; Dorsal soft rays (total): 7; Anal soft rays: 12 - 14; Vertebrae: 35 - 36. Differs from its congeners in possessing a colour pattern consisting of a pale midlateral stripe and two pale oblique bands on the sides of the body; no other congener exhibits a distinct pale midlateral stripe. Can be differentiated further from all congeners except Pseudomystus breviceps, Pseudomystus bomboides, Pseudomystus flavipinnis, Pseudomystus myersi, Pseudomystus siamensis, Pseudomystus robustus, Pseudomystus sobrinus and Pseudomystus stenomus in having a deeper body (17.8-21.0% SL vs. 9.0-17.0). Differs from Pseudomystus leiacanthus in having two (vs. one) dark narrow irregular bars on the caudal fin, longer pectoral spine (19.3-22.4% SL vs. 15.2-18.6), longer caudal fin (33.5-40.0% SL vs. 25.7-31.9) with pointed (vs. rounded) lobes, longer nasal and maxillary barbels (63.1-81.1% HL vs. 31.3-51.5 and 86.2-125.3% HL vs. 70.9-91.3 respectively; nasal barbel reaching to dorsal insertion of opercular flap vs. to just beyond posterior orbital margin and maxillary barbel reaching just beyond base of last pectoral-fin ray vs. to base of pectoral spine), a straight ( vs. crescentic) premaxillary tooth patch, a more sharply tapering snout when viewed dorsally and an even (vs. slightly convex) predorsal profile. Occurs in floodplain channels and peat swamps with very acidic (pH 3.5-4.5), tannin-stained water. Named for the author Heok Hui Ng.

Pseudomystus heokhuii
Dorsal view