Eirmotus

Typically inhabits slow-moving, shallow, shady rainforest streams and swamps with dense submerged and marginal vegetation. The conditions are often rather turbid and the substrate composed of mud or fallen leaves, twigs and branches. Such environments characteristically contain soft, weakly acidic water and are often dimly-lit due to the rainforest canopy above. The fish are found sheltering among overhanging tree roots and aquatic vegetation.

E. octozona can be told apart from congeners by the following combination of characters: bar 1 present; presence of a large and distinct black mark anterior to anus, visible in lateral and ventral views; simple dorsal-fin rays black, sometimes extending onto first branched ray; other rays hyaline or with diffused chromatophores on last dorsal-fin ray, adjacent to upper extremity of bar 6; 25-31 serrae on last simple dorsal-fin ray; uppermost ray of pectoral-fin with faint black margin; width of bar 5 equal to 1-1½ lat...