Here's an article on ich by University of Florida IFAS extension:
FA164/FA164: Cryptocaryon irritans Infections (Marine White Spot Disease) in Fish
Excerpt from the summary section:
"A number of factors determine how severe the disease and mortalities will be and the length of the parasite life cycle. These factors include the strain of Cryptocaryon, the temperature and salinity of the water, the species and age of the fish and their general immune status, previous exposure to the parasite, the number of infective parasites present, and the dissolved oxygen concentration of the water. The life cycle can last from 6–11 weeks, but an average parasite life cycle appears to be 1–2 weeks. However, because the time required until release of infective theronts after tomont formation varies so widely, prolonged treatment periods (3–6 weeks) are recommended. Longer treatment time may be necessary.
Treatments recommended in this publication for any given outbreak should provide significant mitigation of disease. Copper sulfate pentahydrate appears to be the most effective treatment to date. Chloroquine and salinity, as well as formalin, have also proven to have some effectiveness. If the Cryptocaryon strain affecting your fish is tolerant of low salinity, however, hyposalinity will not be an effective control. "
FA164/FA164: Cryptocaryon irritans Infections (Marine White Spot Disease) in Fish
Excerpt from the summary section:
"A number of factors determine how severe the disease and mortalities will be and the length of the parasite life cycle. These factors include the strain of Cryptocaryon, the temperature and salinity of the water, the species and age of the fish and their general immune status, previous exposure to the parasite, the number of infective parasites present, and the dissolved oxygen concentration of the water. The life cycle can last from 6–11 weeks, but an average parasite life cycle appears to be 1–2 weeks. However, because the time required until release of infective theronts after tomont formation varies so widely, prolonged treatment periods (3–6 weeks) are recommended. Longer treatment time may be necessary.
Treatments recommended in this publication for any given outbreak should provide significant mitigation of disease. Copper sulfate pentahydrate appears to be the most effective treatment to date. Chloroquine and salinity, as well as formalin, have also proven to have some effectiveness. If the Cryptocaryon strain affecting your fish is tolerant of low salinity, however, hyposalinity will not be an effective control. "

