Ceramic frag racks?

My mom does ceramics as a hobby and she has some stuff to make it.. like a kiln or whatever it is (I know nothing about the hobby) used to heat the ceramic.

I know there are a few companies that offer ceramic frag racks, but I am wondering if there is a special kind of ceramic that should be used?

My mom says that unless the piece is glazed (I'm assuming like a clear coat) she said it's going to become pretty week from not being sealed from water, and also will leach stuff into the water.

 

I think once sealed properly it should be fine. The magnets on my frag rack or ceramic coated and there no issues. Also, manner impeller shafts are made from ceramic so I would assume it's fine to use in your tank as long as it's sealed properly.