Why am I getting this algae?

I've convered to the BBB and since doing so I'm finding that I'm seeing algae. Please see the linked picture for a better idea of what I'm talking about. I get this about every four days. Vaccum it away and it's back in a few days. I never saw this when I was using the pool store method, although that's probably because I was shocking once per week on that regimen. :) I'm getting this around the perimeter (as pictured) and also in the creases in the deep end (25,000 gallon vinyl). Also, I've found that though it's not highly visible, I can stir up a cloud if I push the brush across most of the flat areas in the pool.

https://lh5.googleusercontent.com/-Z...s800/algae.jpg

I have been on top of my numbers and check faithfully every day. CYA is about 60, I run FC usually between 7-9, CC always 0, pH steady at 7.6.

Thoughts? Recommendations? We've had lots of rain here in Philadelphia and I plan to shock after the hurricane comes through this weekend, but I'm curious to learn why I'm seeing this algae despite keeping up with my chemicals. Is this just par for the course and means that I need to bring the FC up to shock level?

Thanks.

Looks like mustard algae, which can be highly resistant to chlorine.

It will go away IF you raise the chlorine high enough AND brush it. With a CYA equal to 60 ppm, that means taking your chlorine to 20 ppm, and brushing while it's that high.

Also, it looks like your eyeball may be angled toward the surface. If you don't have a main drain, then it's quite possible you've accidentally created a no-circulation zone in your deep end. Ironically, the presence of algae in that location pretty much suggests your pool is not getting a lot of active use.

So, do this:
#1 - Run your pump 24/7 till the algae has been gone for 5 days.
#2 - If you don't have a main drain, adjust your eyeballs so that you get circular flow, angled down somewhat, throughout the pool. If you DO have a main drain, make sure the valve is open.
#3 - Raise your chlorine level to 20 ppm by adding bleach in the evening, and then brush the algae.
#4 - Hold the chlorine above 10 ppm for at least the next 5 days.
#5 - If your pump is on a timer, once you re-enable the timer, make sure to create TWO periods of circulation that total at least 8 hours together.

By the way, the 'BBB Method' doesn't preclude shocking -- as you'll see, we have shock doses listed in the 'Best Guess' chart! In late summer, with very hot water in many parts of the country, and with a summer's build up of algae fertilizer, higher than normal chlorine levels are needed.

Also, if you are testing with anything other than a Taylor based testkit . . . all bets are off, since we really don't know WHAT your pool levels are. (LaMotte makes a kit too, but it's over $200 retail and I haven't seen much evidence that they sell many of those.)

Thanks a lot, Ben! I will follow your instructions just as soon as Hurricane Irene moves on by. I appreciate your insight and recommendations. I've tried to do as much reading as I can to orient myself to the BBB. I'd been using CC as a gauge for when to shock, but we've had so much rain here lately and the pool hasn't been used much in the past few weeks so my CC has remained at 0 and I haven't had the pool at shock level in about a month. Prior to the BBB, I was literally shocking once a week whether it was needed or now, so I think that had a lot to do with why I didn't have algae before. Also, I do have a main drain (open) but do have my eyeball pointed toward the surface. I will readjust it down into the deep end to see if that helps.

Lastly, I have followed your advice and I purchased a Taylor FAS-DPD kit through your Amazon link. I love it! I test daily and have been on top of all of my numbers all summer. I haven't stepped in a pool store since early in the season.

Thank you.