Quote Originally Posted by stevetuck View Post
Can someone help me understand why I would have some yellow algae on the walls but still test acceptable to high chlorine levels?
Typically, the answer would be, "You've accepted the pool industries erroneous information about what 'high chlorine levels" are.

Resolving the problem -- typically -- requires accurate testing of your stabilizer levels, and then adjustment of your chlorine level to correspond. Often, eradicating mustard algae requires sustaining chlorine levels that are 20 - 40% of your stabilizer level. There are other ways; for example you can use sodium bromide to create an unstabilized residual, but often the alternative are an unnecessary complication.

Implementing this solution requires that you first get accurate CYA measurements and then that you acquire the capability to measure chlorine levels outside the 0 - 3 range in which typical color match tests are accurate. 'Guess-strips' are not accurate, and tend to provide random results for TA and CYA values.

You can find the info you need by following the links in my signature to the "Best Guess" page, and the test kit info page.

Good luck, and thanks for subscribing.