Black Algae?

[mistrezbutrfly]

I have been slamming my pool trying to get rid of algae but it does not seem affected by it. I still have blackish greyish blue sand looking particles that keep coming back in clusters every couple hrs. I add more bleach to raise the fc levels to shock level. I have been scrubbing once a day. When I sweep a grey cloud comes up. The pool water looks crystal clear and not cloudy. The sand is always there. I am going to perform the oclt tonight but wanted input on whether I was dealing with black algae. I was waiting for this algae to clear up so I could shock it for the mustard algae. Should I change tactics and try and get the mustard algae first? We got the pool last year in a mess and slamming worked great to clear it up but it was very cloudy during the process so I think that is part of my confusion.
ph is 7.4 CYA is 40 Fc is 17 CC is 0 right now. It's a 22,000 vinyl pool.

 

[duraleigh]

First off, I doubt you have black algae. That normally occurs in gunite pools that have been badly neglected over a period of time. Your description just doesn't fit.

What does fit is that you likely have DEAD algae that is settling to the bottom of your pool and must be brushed up so the filter can catch it. Your SLAM numbers look good but are you running your pump 24/7, backwashing when you get a 25% pressure increase, and brushing as needed.

It sounds like you do not have an auto-vac so brushing that stuff up into the circulating pool water (or manually vacuuming it) is the only way to get it to the filter so it can be filtered out.

 

[duraleigh]

Why do you think you have mustard algae as well?