Did someone here suggest a skimmer sock for you? They definitely won't remove algae.

Cellulose fiber may gum up your sand, but you can remove it when you work on the filter. Doing so is a pain on top mount filter -- you have to cut the plumbing, before you can unscrew the valve!

There's a good chance your pump is too big for your filter, and has been blowing sand out every time your backwash. You'd have to give us actual pump and filter model numbers to be sure.