I'm aware metal alloys of any kind are a no no for salt tank's, especially copper. My question is .....what magnets are safe for reef tanks? I was thinking of making some frag rocks to fix to back of aquarium glass. I can coat and seal the magnet in a dip plastic, epoxy or in a clearcoat. I wanted to know the difference with ferrite, neodymium or iron ect?.... What type of magnet is used in the MP40 for example? ....are they coated in a clearcoat or an alloy that's none corrosive in salt water?