I haven't seen this old thread come up in a while! I can update it by saying that I started using the travertine tiles (shown in this thread) about 2 months ago, after my recent move to Florida. I also replaced the Red Sea Reefer 170 with an I.M. 100EXT. I'm happy to say that an ICP test that I ran a couple of weeks ago showed no tin or any alarming level of any element!