What paint to use?

[daniella3d]

Krylon Fusion is not toxic once dried. I painted the pipe for my overflow with it and no side effect with fish and corals.

Also you can check plastic dip paint. It can be pealed off when it's dry.

Usage:

Animal and outdoor environment applications for PlastiDip protective coating include underwater acoustics, sharp edges, cable stems, cage floors, underground storage tanks, aquariums, iron bars, cable ties, crank baits, junction boxes, fishing sinkers, solder lugs, lobster and crab traps

http://www.plastidip.com/industrial_...ons/Plasti_Dip

Plasticdip would probably work very well to coat magnet to be used inside aquarium. I never tried it though.