Method for site-specific application of a topical medicant for fishes, amphibians, reptiles, and aquatic macroinvertebrates applied in a site-specific manner for the localized treatment of skin wounds, lesions and diseases. The medicant comprises a hydrophilic carrier with an antimicrobial therapeutant formulated as a water-soluble resistant, hydrated gel or dry powder that hydrates and gels on contact with a moistened integument area.