Formalin (Formaldehyde) is a highly active chemical best used in combination with Malachite against most single-celled parasites including white spot, Costia and some skin worms. Do not use in combination with salt. Application: 16 ml per 1000 liters of pond water. Do not use below 10 ° C. Treat up to 3 times at 7 day intervals. If used in combination with Malachite, mix first and...