I have always used a quat algaecide (Alkyl (50% C14, 40% C12, 10% C16) Dimethyl Benzyl Ammonium Chloride). I usually add some every week. Does it evaporate after a while or where does it go? Does it just build up if it doesnt get used up or what? Is there any side effects to it? I am also curious about the same with a polyquat algaecide.