I've never used it, but from what I've read here, polyquat is only a preventative and will not aid in killing the algae. I had an algae bloom last week after a lot of dirt and organic stuff washed into the pool during a torrential rain. Just use bleach to boost your CL level to about 25-30ppm and keep it that way for 2 or 3 days while running the filter 24/7 until all the algae is dead and gone. Then resume using polyquat if you want to, or just rely on bleach to keep it away. That's all I ever have needed except for the unusual occurance I had last week. Just keep swimming,swimming,swimming.....
Hal