mcrab, i understand what you are saying, sea water has minerals and many metals in it, in small quantities, but i have read a lot of stories about dying corals, inverts, anemonies all because they had a small penny, nail, screw, blade that fell in sump and rusted, maybe we are overexagerating here and everything could be fine but i rather not have anything rusting inside my tank that might cause a problem down the road, just a tought.. i need to get my camera to take pics of new magnets