I keep getting algae. cya 50,ph 7.6,alk 90,cal 30. 33000 gal pool,vinyl liner. I keep my cl at 7ppm. At night I raise cl to the top limit of 9 ppm. I use the TF100 pool test kit. The water is crystal clear but there are algae patches on the bottom of the pool and some on the deep end wall slopes. Frustrating to the limit. Don't know what else to do. I follow your advise and no other. Thought about going back to tri chlor and their shock method but I am so happy with the water clarity and no issues with pool equipment and liner longevity which is now 7 years old. Please help me if you can.THANKS