Formalin 30% is a very active chemical and is best used with Malachite for the effective treatment of most single cell parasites including white spot, costia, and some fluke infestations.  We do not recommend the use of Formalin with any salt in solution.  For use above 10 degrees C (50F) dosage 75mls per 1000 gallons.  The normal course is 3 treatments, 5-7 days apart.  Formalin is a very addictive chemical and is best used with Malachite Green for the effective treatment of most single cell parasites, including white spot, costia and some fluke infestations.