For this product we require a completed Drug & Chemical Affidavit on file. If you have not submitted this form to us, please click here, and fax (813-671-8237) or email (fishsupplies@verizon.net) back to us. Thank You. Malachite Green is a dye commonly used as a paraciticide, bacteriacide, fungicide and protozoacide. It is often mixed with formalin and used to treat ich. Caution! It can be toxic if improperly used in treatments.