15 minutes is usually enough.

Most pool algaecides are safe to swim in after 15–30 minutes with the pump running. The chemicals disperse quickly, and the concentration is low enough that it won’t irritate your skin or eyes.

That said, check the specific product label. Some heavy-duty algaecides recommend waiting 2–4 hours or even until the next day. If you’re using a copper-based algaecide, it can stain swimsuits, so waiting a bit longer doesn’t hurt.

Run the pump during the wait to circulate the stuff. If the label says “do not swim until clear,” follow that. Otherwise, jump in.