I find that by using some polyquat (poly 60 type algaecide) at prevention levels, which is about 2 ounces a week per 10,000 gallons, I prevent the late summer bloom I used to get. I start using it in late July or the beginning of August and use about a quart for the summer. If you buy a larger jug, the rest can go toward closing. I keep my chlorine between 2 and 5 ppm most of the time with cya of about 30.