What is the best way to remove calcium scale from pool tiles?

For light to moderate buildup, try a pumice stone first — wet the stone and tile, then gently rub; it won’t scratch glazed ceramic or glass tiles. For thick or crusty scale, use diluted muriatic acid (10:1 water to acid), let it fizz for 30 seconds, scrub with a nylon brush, and rinse. Test on an inconspicuous spot first, especially on natural stone or salt-finished tiles. Avoid wire brushes, razor blades, or harsh pads, and never mix acid with chlorine.