Along with the right temperature range, pH, flow, and other factors, fish depend on protection from disease. Enter the antibacterial and antiprotozoal medication metronidazole, which comes highly recommended as a treatment for a variety of internal and external protozoans and against harmful anaerobic bacteria. Cichlids are very susceptible to the Hexamita gut parasite, which is normally present in small numbers but can spread when stresses lower immune responses. Symptoms can include loss of appetite, dull eyes, and white, stringy feces. Treatment with metronidazole, either mixed with food or added to the tank, is highly recommended, along with water change of at least 50 percent. Metronidazole is also recommended for quarantining new fish. Like great art, an aquarium rewards close observation, and a loving eye will in turn ensure the health of your collection.