Stegastes nigricans
Stegastes nigricans, the dusky farmerfish, is a species of damselfish found around coral reefs at a depth of one to 12 meters, in tropical climates between 30°S and 30°N. They are known for farming monocultures of algae such as cyanophores and rhodophytes. It has an average length of 9.0 cm, but can reach lengths of 14.0 cm. It has 12 dorsal spines, and 15 to 17 dorsal soft rays. It also has 2 anal spines and 12 to 14 anal soft rays. Adults are generally brown, with the dorsal parts of the head and nape being darker, grading to tan on the lower parts of the head and breast. The scales have darker brown margins. The lips are whitish, the suborbital is mostly blue, and the preopercle and opercle scales have blue centers. The median and pelvic fins are brown, the pectorals are dusky, and sometimes there's a well-defined dark brown or blackish spot at the base of the posteriormost dorsal rays, which distinguishes it from  the S. lividus, where the spot is diffuse. When males are in courtship or guarding their eggs they have a broad white bar across the middle of the body and a pale blue stripe from the mouth to the upper part of the pectoral fin.