Aquasonic Formalin Malachite Solution is a dual-action medication that combines formalin and malachite green to effectively treat external parasites such as white spot, skin and gill flukes, as well as fungal infections in freshwater aquariums. It helps clear slime, lesions, and visible fungal growth on fish while preventing secondary infections. The treatment is copper-free and intended for use in fish-only systems, as it is unsafe for invertebrates. Typical dosing is around 5 mL per 20 L of aquarium water daily over several days, ensuring adequate aeration during treatment.