Identification help? Algae or no?

[ccurtis74]

2nd year pool owner. First year on TFP. 6 days into my first SLAM. Pool water looks great. Overnight loss test last night showed 0 FC loss. CC has been less than .5 since day 1 of SLAM. CYA is at 80 so I’ve had to be keeping high FC for SLAM. At least 31FC but the past 36 hours I’ve been at 38 or higher. But I still have these spots of this yellow / brown ish stuff in the bottom of the pool. It’s only on the bottom in the small creases in the vinyl liner. I can run my robot vacuum and it’ll be gone. If I brush it with the brush it just poofs and goes away. Then 24 hours later it shows up again. Am I still dealing with active algae or something different? Shall I stay at the higher FC or go to full 60% or CYA for 24 hours?

Thank you in advance.

 

[Mdragger88]

Does it seem to “bleach out” at higher fc levels? If so it may be mustard algae. The cure is to pass all 3 end of slam criteria then raise to Mustard algae fc slam level for 24hrs. & follow the ma protocol here

Mustard Algae

Today We are going to show you how you can get rid of mustard algae in your pool. By following the steps in this guide and with no expensive chemicals.

www.troublefreepool.com

Or it could be some really fine dirt - but raising to ma slam level isn’t terrible if you’re already at reg slam level & wanna eliminate the possibility of ma for peace of mind.
I thought it was fine clay dirt so i ended slam & it grew … when i went to ma slam level it turned white/grey & once vac’d to waste never returned.