Ideally, you want to prevent algae from ever showing up in your pool in the first place. But we understand, things happen. If algae – be it green, yellow, or black – has taken up residence in your pool, you’ll want to do the following things.
First, brush and vacuum. It’s the difficult, manual labor part of the job, but at this point, it’s necessary. Manual vacuuming bypasses the filter so the algae won’t recirculate. And nothing beats a vigorous scrub of your pool walls to really allow that sanitizer to do its job. Make sure your pump and filter are working properly, and backwash if you think it’s necessary.
Also, if algae has been a persistent visitor, you may want to consider draining the pool and starting all over again. But once again, this is really tricky business, so it’s best to consult a professional at this point.