Have a problem with recurring algae; has been a problem last 3 years and seems worse this summer. Never had any problems before that (for 25 years), and am following same maintenance as before. What happens -- green algae shows up on walls and bottom of pool; I shock, brush entire pool and then vacuum dead algae to waste over next day or two. 7-10 days later, starts all over again with new green algae on walls, pool bottom. This latest cycle, I have been following TFP's advice on how to shock, maintaining shock FC at greater than 28 (CYA is 60 - 70) and testing early in morning for any FC loss. Have had drop of 3-4 FC ppm each of last 2 mornings, although water is clear with no visible algae. I have noticed areas of my liner (23 years old) which appear to have a slight greenish color (it's supposed to be blue) and wonder if algae could have become ingrained in the liner? I'm using 3-inch tabs for daily chlorination (via inline chlorinator which I just replaced), and use 6% bleach to shock. Other readings: ph 7.0, TA 70, CYA 60-70. I am at a complete loss!! HELP!