Quote Originally Posted by chem geek View Post
If this "yellowish-brown stuff" is yellow/mustard algae, then instead of a minimum FC level of 7.5% of the CYA level (which keeps away green algae), it takes a minimum FC level of 15% of the CYA level to keep this algae away. At a CYA of 80 ppm that's an FC level of 12 ppm to keep this algae away from being reintroduced.

Also, the shock level for yellow/mustard algae is higher than for green algae, but with such a high CYA level it's probably impractical. You should also make sure that the yellowish-brown stuff isn't dirt or pollen though it does sound like algae.

Richard
I'm fighting the same battle, vacummed to waste last night and shocked for good measure. Today at noon the brown on the bottom is back but not as bad. Are you saying that the CL level should always be kept at 15% once Mustard Algae has been present?

Wayne