Sterazin is used or the control of gill and body parasites which cause fish to flick when no symptoms are visible to the unaided eyer sterazin will also aid the control of internal parasites such as round worm thread worm and intestinal wormr in order to destroy the parasites in all stages of their life cycle you will need to use the product on days 1 3 6 8 and 10r sterazin may also be used to aid the sterilisation of aquatic plants and is highly biodegradabler do not use when crustacea