What materials are inert in saltwater

[phi delt reefer]

fired clay should be fine as long its not painted. There is a guy/sponsor on Reef2Reef (gooch)that sells rock like clay structrures and frag racks that are made of clay. I think his business is called Alternative Reef? Try googling that.

I have seen one tank with driftwood. The guy clear expoxyed the entire piece before putting it in the tank. I dont know if it was necessary but it seals the woods from leaching out anything or possibly degrading.

glass/acrylic/pvc/neoprene/rubber/vinyl are also safe.