Pool shock and algaecide don't mix well.

You shouldn’t add them at the same time. The chlorine in pool shock will often break down the algaecide or make it foam up, which wastes your money and doesn’t kill the algae any faster.

The typical order is: shock first, let the chlorine level drop back to normal (usually 1–3 ppm), then add the algaecide. That can take anywhere from a few hours to a day depending on sun exposure and bather load. If you’re in a hurry, some algaecides claim to be chlorine-compatible, but I’d still wait a few hours to be safe.

One exception: if you’re using a non-chlorine shock (potassium monopersulfate), you can often add algaecide right after. But read the labels—manufacturers usually spell out the sequence.

Basically, treat them like two separate steps, not one. Your