For pool tile calcium scale, try a pumice stone first.

Pumice stone. Wet the stone and tile, then gently rub — the stone abrades the scale without scratching glazed ceramic or glass tiles. Works great for light to moderate buildup.

If the scale is thick or crusty, switch to a diluted muriatic acid (10:1 water to acid). Pour it on, let it fizz for 30 seconds, then scrub with a nylon brush and rinse. But test on an inconspicuous spot first — some tiles especially natural stone or salt-finished finishes can etch.

Avoid wire brushes, razor blades, or harsh abrasive pads. They’ll leave permanent scratches. And never mix acid with chlorine or other pool chemicals — that makes toxic gas.

If you’re not sure what your tiles are made of, start with the pumice stone. It’s cheap, safe, and you can buy one at any pool supply store for like eight bucks.