When to use . Certain species of parasites such as trichodina, costia, oodinium and flukes can cause fish to produce a whitish mucus layer, known as velvet or slime disease.. Use when fish appear to be covered in a whiteish film, have damaged fins, show signs of irritation or are gasping at the surface.. How to use . Calculate the volume of your aquarium in litres length x width x depth in cm 1000 . Alternatively, use our dosage calculator to help you. Shake the bottle thoroughly before use.. Mix required dose of treatment with 1 litre of aquarium water.. Add slowly to aquarium.. Warning:. This product contains copper, which will kill snails, shrimps and other invertebrates, use half dose in the presence of copper-sensitive species.. Specifications. Composition. Active ingredients: copper sulfate 400 mg 100 ml, formaldehyde 250 mg 100 ml