Fiberglass - worried about scratching?

[GrandizerGo]

Any concerns with using a brush on fiberglass pools? Anyone notice fine scratches? I think about how I treat my car and have only used microfiber cloths.

Also, are there any robots that are good at climbing stairs? I have the Dolphin Echo that came with my pool and I cringe every time it approaches the stairs.

 

[Texas Splash]

I would stick with a nylon brush. That should be plenty stiff enough for your gelcoat.