Protozoans are complete, single celled organisms.
Cilated protozoans possess tiny cilia which allow them to move about and collect food. The protozoan responsible for White Spot Disease is a cilated protozoan large enough to be seen without a microscope. It is of Ichthyophthirius multifiliis in freshwater or Cryptocaryon irritans in salt water. During the early stages of an outbreak, fish will scratch themselves on rocks or substrate. Within 24 to 48 hours, salt like granules appear on the fins and body of the fish.