We didn't take our pool down over the winter,but we kept it covered. When we removed the cover we had clear water but also had heavy algae on the sides and bottom. Everyone said to shock it pretty good,so we did. We have a cartridge pump (small) for now,we're waiting for our new one,but we also have the saltwater system filter. Which is helping but the problem seems to be the dead algae is really fine and when we try to vacuum it goes right back into the pool. All of our levels are ok except for the CYA ,and I don't know how to get it up.