When a swimming pool or spa are brand new all the interior surfaces are smooth.
You should try hard to keep it that way.
Regular cleaning and proper water chemistry are the best way.
These kind of things are not a good idea.
Abrasive cleaners, harsh scrubbing pads, and wire brushes are not recommended.
Never on fiberglass pools or hot-tubs, never on vinyl liner pools, never on any swimming pool tile.
Abrasive does not even mean CLEAN it means “sand away”.
That leaves etching, etching leaves little microscopic shelves to collect junk.
Cleaning regularly, including brushing with a nylon brush combined with proper water chemistry will do the trick.
Every square inch of your swimming pool should be brushed weekly with a nylon brush.
The water line should be scrubbed. Even if it looks fine.
But only with the nylon brush or a sponge.
Skimmers should be scrubbed inside and out.
Stair panels on vinyl liner pools, even the clean ones.
This is preventative maintenance.
You never feel the need for a strong cleaner if you never get a nasty build up.
You wouldn’t use those things on your car finish.
You wouldn’t let it get so nasty you needed to either.
These steps combined with proper water chemistry and a dose of swimming pool enzymes will keep your swimming pool smooth.