Formalin 30% Formalin 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. It is fast acting and used where the time frame does not allow a less vigorous approach. It must be handled with care.
Formalin should not be used with any salt in solution or at and below 10 deg.C. Always read the label.