LIFE CYCLE
There are three phases to the life cycle of this protozoan. Ich is susceptible to treatment at only one stage of its life cycle, so knowing the life cycle is important.
ADULT PHASE: the parasite attaches itself under the mucus layer of the skin or gills, causing irritation and the appearance of small white spots. As the parasite matures, it feeds on blood and skin cells. After some time, the parasite breaks through the mucus layer and falls to the bottom of the aquarium.
CYST PHASE: after falling to the bottom of the aquarium, the adult cyst bursts and divides into numerous daughter cells called tomites.
FREE SWIMMING PHASE: after the cyst phase, the free swimming tomites search for a host. If a host fish is not found within 2 to 3 days, the parasite dies. Once a host is found the whole cycle begins again. These three phases take about 28 days at 70 degrees F but only 3 days at 80 degrees F. For this reason it is recommended that the aquarium water be raised to between 80-86 degrees F. for the duration of the treatment. If the fish can stand it, raise the temperature to 86 degrees. Raising the aquarium temperature in this manner will shorten the length of time between the cyst phase and the free swimming tomite stage. It is during the free swimming tomite stage that chemical treatment is effective in killing the parasite. During this time, whatever you use for treatment should be supplemented with daily or every other day water changes and gravel vacuuming to remove as many adult cysts and free swimming tomites as possible.