The most common disease of aquarium fish; Ichthyophthirius multifilis is a large ciliated protozoan; has a 2-week life cycle. Tomites (liberated by cysts) are susceptible to treatment with malachite green and formaldehyde in combination; tomites embed into fins and scales where they produce many small superficial white papules that lodge the adult phase of the pathogen. SYN: white spot disease (2).
