Apr 4, 2026 cowrie How to Treat Hole-in-Head Disease in Blood Parrot Cichlids: Metronidazole Protocol A white pustule on your fish's head may be hole-in-head disease caused by Hexamita parasites. This guide explains how to identify and treat it with metronidazole. cichlidsdiseasehexamitametronidazoletreatment →