What is this black sticky thing? Is it algae?

[kenichi]

Hi, few weeks ago I went of vacation and forgot to dial up the SWC. I came back with algae in the pool. I did a double shock, brush and the algae was gone. Water is clear, all chemicals seem to be balance for a week now. Started few days ago, I noticed this black thing around the skimmer. It's sticky, gooy tar like substance that I had to use a sponge to remove it. But it comes back rather quickly. The ring would form within a day or so. The pic is showing the ring after few hours.

btw, nobody swam in the pool neither when I discovered the ring, so it can't be lotion or oil.

What is this? Is it black algae? This is new and I had never seen that before for the past 3 years since I got the pool. Please kindly advise.

 

[ajw22]

Welcome to TFP.

Clear water does not mean your algae is gone.

Can your pool pass the Overnight Chlorine Loss Test?

You need your own test kit and follow the SLAM Process to rid your pool of the algae showing up in your skimmer.

Pool Care Basics Archives

Your one-stop shop for all things TFP to include: ABCs of Water Chemistry, Recommended Chemicals/Levels, Test Kits, Troubleshooting, and much more!

www.troublefreepool.com

 

[JamesW]

Looks like typical suntan lotion and body oils.

Maybe people are swimming without your knowledge.

 

[wireform]

It can also happen to be visible if the skimmers don't have enough action meaning it's sharing suction with too much main drain. Had this last week at a pool soon realized someone had tampered with the valves and didn't know how to put them back.....
You can use a tennis ball in the skimmer or on Amazon search for scum sponge to absorb the oils.

 

[kenichi]

Welcome to TFP.

Clear water does not mean your algae is gone.

Can your pool pass the Overnight Chlorine Loss Test?

You need your own test kit and follow the SLAM Process to rid your pool of the algae showing up in your skimmer.

Pool Care Basics Archives

Your one-stop shop for all things TFP to include: ABCs of Water Chemistry, Recommended Chemicals/Levels, Test Kits, Troubleshooting, and much more!

www.troublefreepool.com

I don't have a full test kit yet but I will get one and try the overnight test.
Does that look like algae however? it cumulates rather quickly and I had never seen that in the past 3 years.
Don't know if anything from trees also, I also see these things, look like empty shell of bugs falling to the pool from somewhere. I've never seen that neither in the past 3 years. Don't know if it's related.

 

[kenichi]

It can also happen to be visible if the skimmers don't have enough action meaning it's sharing suction with too much main drain. Had this last week at a pool soon realized someone had tampered with the valves and didn't know how to put them back.....
You can use a tennis ball in the skimmer or on Amazon search for scum sponge to absorb the oils.

I have a dual speed pump, it runs 12h in high speed overnight and low speed during the day. Should I leave it on high all the time? I've never seen this scum in the past 3 years since inception. How can I check the main drain value?