I just assumed they'd be teh safest. They are made more for landfills so I think they may be more lasting that we think. Though it could be the complete opposite in terms of longevity. Cutting a 3-4" plexiglass wall is fine too, I just wanted something I can remove to clean without needing to be so invasive in the tank. I'm going to attempt working on this setup tomorrow. I will goto menards and see what non-toxic trays I can find. I have a few here at home but they aren't labels as either.