frag tiles?

[Myka]

Anywhere that sells tiles for your house. They are used for back splashes and shower floors and come in pre-assmbled sheets, just pull them off the netting. Ceramic and porcelain tiles are reef-safe. I wouldn't use any natural rocks though (slate, marble, granite, travertine, etc) because they could have metals in them.

[sphelps]

I have a ton of leftover scrap natural travertine left over from renos if anyone wants some. It's very porous and pure limestone, I don't believe it would have any metal in it. They are not filled with epoxy or grout like typical travertine either.