Algae Back?

[Tom Tank]

Last week, I did the SLAM and all three tests passed (CC=0, OCLT and Clear Water). Water was perfect green algae gone. Well for at least 5 days. I let the FC level naturally drop to my CYA /FC maintenance level of between 6-11. I woke up today to more algae. Tested everything (using TF100) and the FC was at 8 and CC=0, PH was a little low at 7.2. Also, tested CYA and it was still at 80 (I know it is high). Can anyone help me understand what happened? Is my CYA test off? I tested it several times outside with my back to the sun (multiple times before SLAMMING) and then today. Still reads 80.
I am a new pool owner and converted to TFP method, but now I am nervous that I might not be doing something right. Any advice?

 

[bobodaclown]

It might have gotten below the maintenance level where algae took hold. When you slammed did you brush everything down? Behind the pool light (if applicable)? Anything change with the bather load?

You'll need to keep your FC level a bit higher.

 

[Tom Tank]

I did brush twice a day (morning and night), backwashed the filter. I did not brush behind the light. does this require me to take the light fixture out? I did brush all around the light. I am going to do the OCLT tonight because the water is cloudy now.

 

[jmbradwell]

Yes, you will need to take the light out to check for algae behind the light. Most have a single screw at the top. Remove the screw, tilt the top away from the wall, push down and out and the light will be free.

Hope this helps.

 

[Tom Tank]

I still don't understand how the algae returned. I kept my FC in the right range, test daily, but it still returned. Is my cya readings off?

 

[MBG75]

6 is the minimum. Really shouldn't let it get below 9

 

[Tom Tank]

I will keep FC at 9. When I woke up yesterday, FC was at 8 and the algae was back. So that is the cause of my confusion.

 

[PAGirl]

Is there good circulation?

 

[Tom Tank]

Yes. I have 2 skimmers a main drain and 4 returns. There is not one spot that keeps getting algae. Yesterday it was all over the bottom of the pool. I am pretty much at a loss as to what to do next. I am Slamming the pool now, but when it is finished i am not sure where to maintain the FC.

 

[Kiss4aFrog]

You should go by the CYA /Chlorine chart. The problem is to figure out if it's algae returning or something else like pollen being blown in.

Did you take the light out and clean it and the niche it sits in ?? Have you carefully inspected the water feature to see if there is any area that a pocket of algae could be hiding along with the back of the skimmer doors, inside the skimmer itself and the bottom of the ladder rungs if you have a removable ladder ??

If you pass the SLAM and it is algae coming back it's because a small amount is hiding someplace.

 

[Tom Tank]

Thanks for the advice. I have done what I thought was a good job of brushing the pool - removed light, removed ladder etc... The water is clear now after the second SLAM was completed, I am letting the FC drift to maintenance level. I have added polyquat 60 today and will continue to monitor the pool since I know pquat can eat up FC. First time I did the SLAM, I never removed the light to clean behind it. There was really nothing back behind the light or hiding in the ladder. I hope this next round does it for good. I will keep you posted.