[Disease and Causes] White spot Caused by Ichthyophthirius multifiliis parasite [Symptoms] Small white spots, about the size of a salt grain, on the skin, fins and gills. [Reason for Infection] Stress related. Usually a consequence of poor or incorrect water conditions, fluctuating temperature and general poor husbandry. Sensitive species may develop white spot as a result of being introduced to a new aquarium. [Action] Ensure the water is free of pollution and isolate cause of stress. [Treatment] 
Treat promptly with an anti-parasite medication. It may be necessary to raise the water temperature to improve the effectiveness of the treatment. Wounds left by parasites may become secondarily infected.