My recent experience and ample gut tells me that you should maintain shock levels until your water looks "right". I just went through a similar process with a cartridge filter. It's tough. I wanted to SHOOT anybody that uttered the words "... and then vacuum to waste".

One thing to remember: Keep your eye on the filter pressure. You are pushing a LOT of dead algae through there. When I was in the throes of my algae battle, I was cleaning the filter elements twice daily.

Hang in there. You're in the home stretch.