Bacteria communities living in mucus secretions of common carp Cyprinus carpio (Cyprinidae) were exposed to the organic nanomaterial fullerene (C60) to evaluate its potential bactericidal effects. End points analyzed were viability, growth, reactive oxygen species (ROS) concentration, and total antioxidant competence against peroxyl radicals. Viability was not affected (p > 0.05), whereas growth was arrested (p < 0.05) after 3 hours of exposure to the three concentration of C60 assayed (0.1, 1, and 10 mg/L). Levels of RO measured at different C60 concentration showed that some colonies were reactive (significant dose-response relation, p < 0.05) to C60, whereas others were not. The nonreactive colonies to C60 presented higher antioxidant competence to peroxyl radicals compared with the reactive colonies (p < 0.05). The strains isolated and identified by polymerase chain reaction (PCR) products of 16S rRNA showed a predominance of Aeromonas genus between all the isolated Gram-negative bacteria. Thus, the present results indicate that C60 affects bacterial communities that live in mucus secretions of common carp.