Lernex fights the worms of the skin (Gyrodactylus), the worms of gills (Dactylogyrus), and intestinal worms (Nematodes). Lernex is also effective against leeches (Piscicola), fish lice (Argulus) and anchor worm (Lernea). The presence of these parasites is noticeable to the naked eye. The characteristic symptoms of contamination with these parasites include apathy, rubbing and reduced appetite. 100 g to treat 2500 litres.