I am a big time believer in polyquat.

I have a plaster pool that was mistreated by the original owners and it is rough in areas. I refuse to replaster the pool until it gets significantly worse... When you have rough plaster you have to be on the lookout for black alge. So I have used polyquat as algae prevention for three years. Knock on wood but I have never had a green, yellow, or black algae bloom...

I would add the whole 32oz bottle to your pool as an initial super dose of polyquat.

The only problem with polyquat is the price, normally $20... But I ordered some from Leslies on sale $7.33/quart last month now it is on sale under $5.00. So I ordered 5 more quarts.

Good luck.