Using ceramic magnets in reef tank

I'm trying to make a frag holder for my tank, I would like to use magnets, I saw some ceramic magnets at Lowes and picked some up. they are not coated in plastic, just bare, but they look like the magnets that are inside the maxijet propellers to make them go. Anyone have a clue if these are reef safe?

 

I don't know but they sell stuff at lowes made for dipping the handles of tools in to give them a rubber coating. I was told by a magnet manufacturing company that this is what they use to rubber coat magnets...