Tiny bit of black algae in corner - keep slamming?

[mplate51]

Hey all, after opening and slamming my pool, the water is crystal clear except for one tiny corner in the deep end that looks like black algae. Hitting it with any kind of pressure with the brush is difficult because of how deep it is, but I am able to brush it. Brushing seems to do nothing. During the SLAM, the spot did reduce slightly. Should I keep my FC at SLAM level for this small spot, or let it reduce down to normal levels and jump in to brush it better? I've attached two pictures, one zoomed in and one without zoom just to get an idea of how small it is. Any advice is appreciated - thanks!

Vinyl Pool with SWG - currently off, will turn this on once FC levels reduce
FC is at 14 (this is 2 days after bringing it up to SLAM level of 20)
CC is 0.5
CYA is 50 (will bring this up to 60-70 after I get this spot cleaned up)

 

[setsailsoon]

mplate,

Welcome to TFP! Sorry you're having trouble with black algae but it's often problems that cause new people come here and join up. What chemicals have you added to the pool? Can you please post a set of test results and add your test kit type to the signature? You've come to a great resource. We don't sell anything just have real expert volunteers and experienced pool enthusiasts here to help you solve problems. So advice is never conflicted with desire to sell you something. We do things differently because it's the best lowest cost and effective method to pool care.

Black algae can be stubborn. Have you verified it's black algae and how did you do that? My experience with black algae was the quickest way to get rid of it was during a SLAM scrape it up with a fingernail or piece of smooth flexible plastic. When you do this you expose the live cells that are propagating it. I have a plaster pool not vinyl so you'll also have to be careful not to damage the liner. Patience is key here.

I hope this helps and I'll post some links below that may also help.

Chris
Pool Care Basics

 

[mplate51]

Hi, thanks for the response. I used the TFP method last year and this community has been incredible! My test kid is a T-100 Salt. Below are my latest results. I'm not 100% if it is black algae, just a guess from what I can see and how it is not coming off after simple brushing. How would I verify if it's black algae?

FC = 14ppm (slammed to 20ppm 2 days ago and still coming down as it's been cloudy)
CC = 0.5ppm
pH = 7.6
Alkalinity = 50ppm (planning to raise this to 70)
CYA = 50ppm (planning to raise this to 70)
CH = 75ppm
Salt = 3000ppm

 

[mknauss]

How would I verify if it's black algae?

Scrape some of it off and smear on a paper towel. If green, then it is black algae.

You are sure this is inside the vinyl? There are cases where mold/algae grow outside the vinyl but show through.