What is the best tool for removing calcium scale from pool tile?

A wet pumice stone is your best bet for ceramic or porcelain pool tile. Wet the stone and tile, then rub lightly — it won’t scratch the glaze but will remove scale. Avoid wire brushes, steel wool, or abrasive pads, as they scratch the surface and worsen future buildup. For thick scale, a diluted muriatic acid solution can help, but it’s risky for grout and metal fittings.