4 Things to Know About Using Pool Shock and Algaecide Together

Never add pool shock and algaecide at the same time. The chlorine in shock breaks down algaecide or makes it foam, wasting money and not killing algae faster.

Shock first, then wait for chlorine to drop. Let chlorine levels fall to 1–3 ppm before adding algaecide. This takes a few hours to a day, depending on sun and pool use.

Non-chlorine shock is an exception. If using potassium monopersulfate shock, you can often add algaecide right after. Always check the label for the correct sequence.

Treat them as separate steps. Even if an algaecide claims chlorine-compatibility, wait a few hours to be safe. Rushing wastes product and effort.