Hello,
This may not be the best place to post this but I figured I would try. I have a 10000 gallon fiberglass pool that is 2 years old. Recently we had a film develop on the pool walls and floor. The walls scrubbed clean easily with a magic eraser. The floors however are hell to get clean. It's a black grime the has made the floors almost sticky meaning you can't slide your feet. If I scrub the hell out of them with the magic eraser, it cleans like normal but it's not feasible to do the whole floor.
Pool guy came out and said I needed stabilizer and my chlorine was low. He also said my phosphates were 1500ppm. He treated my phosphates and turned up my saltwater generator. Pool is crystal clear. We do get a lot of plant debris but I do a good job keeping up with that.
It is a saltwater pool. Any thoughts on the cause of this and how to remove the grime off of the pool floor? He mentioned possibly An enzyme cleaning and is bringing another guy out for a second opinion.
Pool is serviced weekly.

Try posting on troublefreepool.com

Very helpful pool gurus on there.

You have pool tar. Fiberglass pools are notorious for this. It can come from several different sources, propagated by your chlorine reacting with a different chemical in the pool, (usually sunscreen). bioguard will help with this in most cases, will go away with time if you keep balanced.

add CYA until you get is stabilized. I'd bet money you probably need to add acid, but check your PH to verify. Once you do this, shock and brush and vacuum, rinse and repeat and you should be good to go.