Grey algae?

[pzampino]

I am a first-season pool owner, but thanks to these forums, I've had a mostly trouble-free pool all season. I did have to apply the SLAM procedure back in July to knock out some algae that had gotten away from me, and it worked just as described.

However, I've been recently facing a grey substance, which at first I did not think was algae because of the color. However, I've been SLAMming my pool for about a week now, and this grey substance persists. I've been brushing and vacuuming, and maintaining a shock level FC.

TA 90
CYA 70
FC 28 (I add chlorine every night to get it above 28, up to 32ppm)
CC ?
pH 7.6

My last two overnight FC loss tests were 1.5ppm, so is this really algae? Any suggestions?

Bottom right corner, and on slope (left side of photo)

 

[pooldv]

Is it slimy or rough?

 

[PAGirl]

I've seen algae get sort of bleached out when it dies and settles to the bottom. But, as asked above, it would depend on what it feels like.

 

[pzampino]

Hmm, I'll have to scoop some out with the net to check the texture...

 

[pzampino]

Hmm, I'll have to scoop some out with the net to check the texture...

It was difficult to pick up, but on the steps, it seemed more gritty than slimy. The steps weren't slippery at all.

And, it's still here :-( ...

TA 90
CYA 70
FC 34
CC ?
pH 7.6

 

[pooldv]

Definitely doesn't seem like algae. Does it seem stuck to the liner? Or is it gritty dirt that is landing there? Is it mostly in front of the returns? Here are some possibilities that come to mind.

Sand/dirt from filter if there are issues with the spider gasket or other problem
Scale from the SWG cell, get some of it and put some acid on it and see if it fizzes and dissolves
Dirt/sand from another source outside the pool. We recently had some ants messing around under the coping and there was some sand in the pool and we don't even have a sand filter.
Scale build up on the liner, but your pH/TA don't currently indicate that scaling is likely. If your pH spends some time above 7.8 regularly then it could be scale.

 

[pzampino]

Definitely doesn't seem like algae. Does it seem stuck to the liner? Or is it gritty dirt that is landing there? Is it mostly in front of the returns? Here are some possibilities that come to mind.

Sand/dirt from filter if there are issues with the spider gasket or other problem
Scale from the SWG cell, get some of it and put some acid on it and see if it fizzes and dissolves
Dirt/sand from another source outside the pool. We recently had some ants messing around under the coping and there was some sand in the pool and we don't even have a sand filter.
Scale build up on the liner, but your pH/TA don't currently indicate that scaling is likely. If your pH spends some time above 7.8 regularly then it could be scale.

I've not suspected sand because I've been failing the OCLT (-1.0 to -1.5), and assumed it's something biological.
As my last post indicated, I've increased the FC level to see if that helps. Once the threat of thunderstorms passes, I'll get in it for a closer look where it accumulates in the greatest measure.

Thanks for the suggestions.

 

[pzampino]

Well, it looks like it was algae. Either it was a really strong variety, or I'm not measuring my CYA accurately, but I had to crank the FC up to 40ppm to finally beat it. No more signs of algae yesterday, and it passed the OCLT last night.

 

[pooldv]

Nice! Pool looks great!

 

[pzampino]

Thanks! These forums have really helped to make my first season as a pool owner a good experience.