Green algae keeps coming back

[finn_]

Hey everyone,

Relatively new pool owner here and trying to get my pool to stay algae free has been a bit of a struggle. I did a SLAM ~2 weeks ago, pool has looked great ever since. Today, I noticed some green on my pool cleaner again (easier to see it on the white surface than it is on the pebbletec). I've been pretty diligent about keeping the chlorine level good since the SLAM so this was disappointing to see. Here's my latest test results from the TF-100:

FC 8
PH 7.8
TA 90
CH 350
CYA 80

I understand my CYA is a little high (previous owner only used tabs), but the lowest the FC has dropped since I ended the SLAM was 6.5 (but only got this low once - has been 8.5+ otherwise). Per the FC/CYA chart my FC has always been above the minimum, so I'm a little stumped as to how there's algae growing again. I'm assuming that I'll need to SLAM again (hopefully a short one). How can I keep the algae from coming back again after the SLAM is done?

Edit:
Phosphates are ~1700 ppb from the last test I had done at Leslie's before I got the TF-100.

 

[HermanTX]

Welcome to TFP.
Thanks for using the SLAM process and posting results.
The first thing that comes to mind is did you pass all 3 criteria before you stopped the SLAM process?
See SLAM Process

The one that gets most people is overlooking the Overnight Chlorine Loss Test
Apparently there is some algae that is hiding. Do you have a ladder? Did you check the skimmer weir doors? Those can be hiding algae.

To end a SLAM
Once all three of these criteria are met, you have completed the SLAM process and can allow the FC to drop to normal levels.
CC is 0.5 or lower
AND your overnight chlorine loss test shows 1.0 ppm of loss or less
AND pool water is crystal clear with no visible sign of algae (dead or alive) on floor and walls

 

[finn_]

I don't have a ladder. I did check the outside of the skimmer weir doors, don't think I checked the inside now that I think about it. My other thought is that it might have been hiding in some of the little corners on the pool vac. There's a lot of little places to hide inside the wheels and by where the hose attaches to the vac. I brushed it down as good as I could last night when I started the SLAM again but theres some places I can't get to still.

The first SLAM did pass the OCLT. This one I'll hold for an extra 24 hours after that to make sure everything is dead. Is it work keeping the FC slightly elevated for a couple weeks after ending the SLAM? Per pool math, recommended FC is 6 - 11. I was thinking about keeping it at 15 for a couple weeks after.

 

[HermanTX]

Holding for an extra 24 hours is good.

Stay on high side of target so 11ppm would be fine.
Going higher is fine but may not be necessary. Remember that you can swim up to Slam level for your CYA