Hi....I am a noobe at pool care. We purchased a home with a above ground pool. Drained water once, treated, but had heavy rains and now it was very nasty and green. Purchased HTH Blue to Green Shock treatment....looks like I need a second application. But it says after treating vacuum to waist. My pump has a vacuum to waist, but wont that drain out all the water? I dont think I want to add a second application of HTH Blue to Green....water is still kinda nasty...what can I do without draining the pool? Thanks.