In communication i had with Tunze ( Roger Vitko and a UK dealer) when they changed from the enclosed coated magnet style to bare magnet style they said the magnets are rust/corrosion proof and made to be used in fresh/salt water. I didn't believe them and chose not to use them, which later appeared to be a wise decision when pictures of rusting magnets began appearing on the internet. Its a shame when a "reputable" company like Tunze can't be trusted and gives out bad information regarding their product