Black algae keeps coming back

wags22 · Aug 29, 2022

I've had black algae for the last 2 years. This year it was really bad at the start of the season and I'd managed to kill most of it. Then my swg died two days ago and today I'm seeing signs of black algae again. Is there anything I can do besides keep scraping tablets over the affected area?

My pool was filled in 2009, and once or twice over the years it's been drained 1/2 way. And depending on how long I leave the cover off, I'm filling it often. Would draining it completely allow me to kill the algae off for good?

proavia · Aug 29, 2022

Post a full set of current test results from your TF-100.
I see you last used PoolMath 2 years ago- or at least that's the last time you saved any data to it.

FC
CC
pH
TA
CH
CYA
Salt
Water temp

Chances are the FC has fallen below minimum. Treat the pool as a non-SWG pool if you don't have a functional SWG in use.
FC/CYA Levels

The calcium (CH) level is possibly quite high also.

Blackalgae is difficult to eradicate from pebbletec due to the nooks and crannies in the pebble finish.
Have a read thru this article:

Black Algae

This guide provides a step by step procedure for eliminating black algae in your concrete or gunite pool. Read full post here.

www.troublefreepool.com

duraleigh · Aug 30, 2022

+1 waht proavia said. Current test results gets us on the same page and we can advise a plan. Without them, we are just stabbing and guessing at fixes.

wags22 · Aug 30, 2022

Ok, did my tests and my levels are all out of whack. But I'll admit that I haven't done much maintenance lately and the swg dying has really messed it up. But here goes:
TA 150
FC 2
CYA 0
CH 250
PH - did not test, but I'm sure it is high like TA since I haven't added muriatic in a while.

I've got a floater in but I've never used one before. How much will it raise my chlorine level and how fast? Does it also add CYA or do I still need to add that separately?

proavia · Aug 30, 2022

We actually need you to test all of these - without a full set of test results, it's still only a guess what is needed.

FC
CC
pH
TA
CH
CYA
Salt - if you have a functional SWG
Water temp

And try to keep them in this order as it is easier for most of us who have been around a while to review.

wags22 · Aug 31, 2022

FC 2
CC 2
pH 7.5
TA 250
CH 250
CYA 0
Water temp 86
Salt level - N/A as SWG is currently out of commission.

duraleigh · Sep 1, 2022

Would draining it completely allow me to kill the algae off for good?

No, but a SLAM followed by proper chemistry will.

FC - too low
CC - too high
CYA - too low.

Please read "Pool Care Basics" up in Pool School. Then, You will need to SLAM the pool by prcisely following the SLAM article again, found in Pool School,