How do I remove white scale on pool tiles without making it worse?

Use a wet pumice stone on glazed ceramic tiles, or a non-acidic cleaner with a stiff nylon brush for glass tiles. For baked-on deposits, use a professional sulfamic acid cleaner exactly as directed. Vinegar will etch grout and stone surfaces. Prevent new scale by keeping calcium hardness at 200-400 ppm and pH at 7.4-7.6.