I’m not so sure I’ve had yellow algae, although my green algae as it started to get better looked a bit yellow. I’m also not sure what the ring is at the bottom of the pool. I can only give you advice from my own experience.

I have town water but I do use a salt softener. The softener does cause the pH to rise, but your problem sounds like you’ve got to put your pool on a shock diet.

When my pool was cloudy, green and brown, after I removed all of the dead leaves, I started adding a bottle or two or three of shock every day and ran the filter 24 hours a day for about a two weeks. My pool was in very, very bad condition.

Try maintaining extremely high chlorine levels for about a week or so and keep the pool filter running. You should begin to see the algae begin to clear up. Additionally, make sure to sweep your pool thoroughly. Sweep the walls, bottom and ladder. You want to dislodge any algae that wants to grow. After sweeping the pool allow the filter to continue running and then vacuum out the pool. Also, after you vacuum the pool, you should give your filter a good cleaning.

The problem you’re having sounds to me that the chlorine levels have been allowed to dip too low. Once they dip too low, algae gets a chance to grow.

A question for you: How many times a day to you test your pool water and what are the chemical levels?