Black Slime in Skimmer

[Sierra54]

I keep getting a ring around the inside of my skimmers just above the water line. I brushed it clean last night and after work I came home and it came back strong in one skimmer and just a few specks in another. It feels like slime but not sure if it may be black algae.

What could I be dealing with here and how can I get rid of this? No oils or lotions used by any swimmers.

 

[Texas Splash]

Kind of like a black gummy stuff that you can smudge & smear right? I refer to that as a scum line. Sometimes it can develop is other areas of the pool once or twice a year. May not necessarily mean you did anything wrong, just a collection of oils, dirt, etc. I use scrub pad or Magic Eraser to clean it. Check your chemistry though to be safe. Your Poolmath lists no tests at all. Post your test results if you want us to review.

 

[Newdude]

The residual swimmer oils/ lotions / etc are likely clear but suck up any crud that passes through the skimmer and it becomes black quick. The oil floats and doesn't get pulled through the filter, so it localizes on the skimmer walls.

You wash your hair, skin and suits and are covered in residuals from that, whether or not you realize it. Then you perspire. Then your skin gives off oils also. There is always swimmer crud, with or without sunblock.

Toss 2 tennis balls in each skimmer and it will likely go away.

 

[Sierra54]

The residual swimmer oils/ lotions / etc are likely clear but suck up any crud that passes through the skimmer and it becomes black quick. The oil floats and doesn't get pulled through the filter, so it localizes on the skimmer walls.

You wash your hair, skin and suits and are covered in residuals from that, whether or not you realize it. Then you perspire. Then your skin gives off oils also. There is always swimmer crud, with or without sunblock.

Toss 2 tennis balls in each skimmer and it will likely go away.

Had to wipe away another layer of black slime in just one of the skimmers today. Took some new measurement also.
FC 7
CC 0
pH 7.2
CYA 40
CH 125
TA 50
Salt 4200

I finished the SLAM about 6 days ago but have been afraid to raise the CYA because I was battling a never ending SLAM last summer and never felt like I successfully killed everything that was leaving a small dusting of dead algae along the seams in the liner. Not sure if it may have been pollen now.

I used skimmer socks this year and have been cleaning and reusing them for about 5 days before swapping the out for new. I think I may still be getting very small spots of pollen but nothing like last year. If it was dead algae wouldn't my CC be 0.5 or greater?

 

[Texas Splash]

If it was dead algae wouldn't my CC be 0.5 or greater?

CC levels don't always correspond to what we would expect to see. They fluctuate on any given day or throughout the day. Your numbers above look quite good, so I would continue with the good chemistry and monitoring.

 

[Newdude]

I finished the SLAM about 6 days ago but have been afraid to raise the CYA because I was battling a never ending SLAM last summer and never felt like I successfully killed everything

Feel free to run an elevated FC for a week or so to ease your mind. With no organic loss, the SWG should be able to maintain SLAM.

Give every hidden in plain sight spot another good once over as well.