I have a crystal clear pool and have been enjoying it this summer. I use the TFP method.
Last year while on vacation, the FC dropped to 0 and there were slight grayish hazy areas on the bottom, which I assume was algae. When I raised the FC to shock level, the areas disappeared. However, since then, the slight haze keeps coming back if the FC drops below 10 or 8. Raising it to 12 or higher causes it to disappear.
This week, I am SLAMing the pool (2 days so far). The FC drop today was around 8 (although it was a bright sunny day, and my CYA isn't very high). So when it dropped below 10 this afternoon, there was the slight grayish haze again. There is never any spots on any other part of the pool, and as I say, the water is crystal clear, the vinyl is 2 years old, and the ladders are clean.
If I am getting rid of algae by SLAMing, shouldn't the algae at least stay away at FC of 10? Could it possibly be something besides algae?
I use FAS-DPD.
Thanks for your help.