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.

Check with some of the major pool manufacturers. Pools have been lined
using tiles for decades. Hell, if it's good enough for the YMCA pool...