Nylon for vinyl, stainless for concrete.

Pick the brush bristles based on your pool surface, not the price tag.

Here’s the short version: if you have a vinyl liner or fiberglass pool, use a nylon brush. It’s soft enough to clean without scratching. Stainless steel or wire bristles will tear the liner and leave permanent marks. Don’t learn that the hard way.

For concrete or gunite (plaster) pools, you want stainless steel bristles. They remove algae and mineral deposits that nylon can’t touch. But check the grade — cheap stainless can rust and stain the plaster. Get 304 or better.

Grout brushes (brass) exist but I’d skip them. They wear down fast and leave metal bits in the water.

A wrong brush ruins your finish faster than algae.