If you have mustard algae, with a CYA of 35, you need to be shocking your pool up to 30 ppm of chlorine (see the best guess chlorine chart link in my sig) and maintaining that until the algae all dies. You also need to thoroughly brush any area that might have the algae in it--light niches, ladder steps, etc because if you leave any of it living, it's just going to come back.
If your pool is in sun for the whole day, you might want to consider raising your CYA, but I wouldn't do it until you have the algae gone, because you want all your chlorine available to work on the algae. Plus, as your CYA levels go up, so does your required chlorine levels (again, check the chart).
Janet
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