How long should I wait to swim after adding algaecide?

Wait at least 15 minutes for most common polyquat algaecides to circulate and mix into the water. Swimming sooner means swimming in a concentrated chemical cloud that can irritate your skin and eyes. Some copper-based algaecides may require 30 minutes or longer — check the label. The real rule is to wait until the chemical has fully dispersed and you can’t see streaks or swirling where you poured it.