Black algae?

[Kkatwilson]

Is this black algae? It’s pretty much only on the Cabo shelf. Should I just continue to scrub with a steel brush daily and high chlorine. Or do something else?

Just looking for a little help. Thanks!

 

[needsajet]

It could be black algae. Try scrubbing with the stainless steel brush, then put a trichlor puck over one patch for 5 or 10 minutes. Don't leave it any longer or it could bleach the finish, but it's OK to repeat the test. Remember that spot and compare after a few hours. If it's algae, you should see a difference vs. the other spots.

How long ago was the plastering done?

Cheers and welcome to TFP!

 

[Kkatwilson]

It could be black algae. Try scrubbing with the stainless steel brush, then put a trichlor puck over one patch for 5 or 10 minutes. Don't leave it any longer or it could bleach the finish, but it's OK to repeat the test. Remember that spot and compare after a few hours. If it's algae, you should see a difference vs. the other spots.

How long ago was the plastering done?

Cheers and welcome to TFP!

Just leave the puck there or scrub with it?

The pool was completed last April. We have blue diamond micro fusion

 

[needsajet]

Oh sorry, no need to scrub with it. It just causes slightly lower pH and strong active chlorine right over the spot. With a new finish, don't leave the puck in one spot longer than 5 minutes.

So for example...

Scrape the test spot and the spots you'll be comparing with the stainless steel brush a few times over, no need to press super hard
Place puck over the spot you're testing
Remove it after 5 minutes
Brush the water around just to eliminate the possibility of acidic water sitting against the pool finish
Check back a few hours later and see if you can see a difference.
If only slight difference, repeat the test.

I got some early black algae on a new finish doing this, but one spot where I left a puck too long showed lighter plaster. You cant see it anymore, but it alarmed me at the time. In the end I was successful and rid the pool of black algae and it's been good since. The spots were all on the bottom, so I did it all with repeated brief treatments with a puck. Throughout the treatment period, I was maintaining FC at 15% of CYA.

Whenever I was brushing, I would throw four pucks in and maneuver them around the pool from spot to spot with the steel brush. My rule of thumb was 5-10 minutes. It took a few weeks of brushing every 3 days and doing this; likely would have been faster if I did it every day.

But first is the test to be sure it's something living.

 

[Bperry]

Is this black algae? It’s pretty much only on the Cabo shelf. Should I just continue to scrub with a steel brush daily and high chlorine. Or do something else?

Just looking for a little help. Thanks!

View attachment 437969

I don’t see anything in that picture, algae or otherwise. Maybe a few white dots but those aren’t black.