Hi, I heard that if algaecide is to be used polyquat is the one to use. Are there any disadvantages or possible health hazards from it? Does it stay in the water for good, break down into something bad or go away? What do you guys think of the Kem-Tek KTK-50-0006 Pool and Spa 60-Percent Concentrated Algaecide? Does it have copper as well or other nasty stuff?