"Harry Muscle" wrote:
Anybody know if porcelain tiles (like the ones that go on the floor) are
safe in an aquarium. Sinks and such are made of porcelain, so the porcelain
itself is fine, but the tiles are colored porcelain. Anyone know what kind
of chemicals they use to color porcelain, and if this stuff would be pretty
well encased inside the porcelain so none of it leaches out? I'm hoping to
use these tiles for a background.

It's going to be very dependent on the glaze. Back when I did lots of
pottery, I had to be pretty picky about which glazes I could use for food
containers (especially pitchers). Lots of the prettier colors used heavy
metals as the pigments -- not good to ingest. If you don't know the contents
of the glaze, you're living on the edge.