Total noob - think we have black algae

[Beastos]

Hi all,

Hoping you can help. We've been through the ringer at Leslies - had been going with the "just do whatever the people at the store tell us" approach to pool maintenance. Worked well enough for two seasons (wasn't super easy on the ol' pocketbook) but this one has been a doozy. My husband is fighting for just filling the sucker in, but I LOVE the pool, so am trying like heck to make the case for keeping it.

We're dealing with what I suspect is black algae - photos attached. Would love confirmation on that. I tried to do the scrape some on the fingernail and smear on paper test to confirm, but the smear was brown and not green.

We've also been remiss on basic pool maintenance. Did a test yesterday and CYA measure was below what our test kit could measure (we have the Taylor 2006c test kit) and don't have any chlorine measurable. (I know I know, not good.)

My general plan was to:
1. Raise cyanuric acid levels
2. Then measure pH, and get it in the 7.2 - 7.4 range
3. Then follow the suggestions here for dealing with black algae, which seems to be not SLAMMING, but keeping chlorine high and just below SLAM levels, while brushing the Darn out of the affected areas.

Does that sound right based on the pictures?

Note we have cracks in our plaster and are getting quotes on replastering (you may see me here again asking questions about that as well). Thanks in advance for all of your wisdom!

 

[YippeeSkippy]

hello Beastos.... can you provide us with a full set of test resuts?
FC
CC
pH
TA
CH
CYA
Salt (if applicable)

Your pool needs chlorine NOW.... long before it needs the pH played with.

You'll have to deal with that performing a SLAM process cause as it stands now your pool is neglected and liquid chlorine and a good stiff brushing often are what is needed.

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

Maddie

 

[Beastos]

Thanks Maddie. Added some chlorine last night (we have the powdered kind from Leslies but just bought liquid). These are the readings I just took:

FC: 0.2
CC: 0.4
pH: 7.1
TA: 130
CYA: 0 (or not measurable, the dot never disappears)

 

[DorsalSpine]

You need to get your CYA level up ASAP. The sun will kill your FC quickly in your climate without adequate stabilizer. Keep adding the liquid chlorine as much as possible. Make sure to top up your FC at night when your chlorine can do its work without the sun degrading it.

 

[YippeeSkippy]

Granular chlorine will add both CYA and chlorine, but as a rule when teaching pool chemistry we like new pool owners to use
single chemical products so they learn the use/response of those chemicals. If you have some granular go ahead and use enough to give you 5ppm of FC. Liquid is preferred, but you're in a bind needing both TODAY.

We want to see about 30ppm of CYA to start your SLAM process and have the FC remain in the water longer than a blink of an eye when you add chlorine and there is *no* CYA.

Maddie

 

[Beastos]

Ok, we have our CYA up between 30 and 40 (hard to say exactly when the dot disappears).

We're adding chlorine sort of haphazardly right now. Should I start an official SLAM process? If I'm recalling correctly the page here about getting rid of black algae says to keep chlorine right below the SLAM levels - could you advise on the right path forward here?

So so appreciative for your help! Have learned so much from this forum already.

 

[mknauss]

Raise your FC to 10 ppm and do a Overnight Chlorine Loss Test tonight. If that passes, then maintain your FC at 10 ppm or so while brushing scrubbing the black algae daily.

 

[Beastos]

Did the overnight chlorine loss test. Went from ~11ppm to ~7.5ppm FC. What's confusing me is that there was no measurable CC this morning. I assumed that's where the lost FC would be. Did I screw up the test, or misunderstand what's happening here?

My CYA is at 50 (I removed my socks with CYA last night and measured this morning).

Should I still try to keep the FC around 10ppm, or do I need to go higher?

THANK YOU THANK YOU

 

[mknauss]

With that FC loss, time to follow the SLAM Process.
Your CYA is 40. Your SLAM level FC is 16 ppm. Read the article. Follow the process. Brush, brush, brush.

 

[cme4oil]

Did the overnight chlorine loss test. Went from ~11ppm to ~7.5ppm FC. What's confusing me is that there was no measurable CC this morning. I assumed that's where the lost FC would be. Did I screw up the test, or misunderstand what's happening here?

My CYA is at 50 (I removed my socks with CYA last night and measured this morning).

Should I still try to keep the FC around 10ppm, or do I need to go higher?

THANK YOU THANK YOU

If your CYA is 50 now, Your SLAM level FC is 20. Follow the SLAM Process as mknauss indicates above.

 

[Beastos]

Thanks both. Have been SLAM-ing since Friday night/Saturday morning, and the pool looks great. The visible algae is gone with the exception of a handful of spots and the water is mostly clear.

Can I get some advice on next steps here? My plan is to:
1. Run the overnight chlorine loss test tonight
2. If I don't meet the stop criteria, I'll continue the SLAM for another day
3. If I do meet the stop criteria, I'll let the chlorine drop to my FC range (looks like 6 - 8ppm with my CYA of 50), and then run the full set of tests.

My two primary questions are:
1. If I meet the stop criteria for SLAMing, but can still see spots of visible algae, am I ok to stop the SLAM? There are just like, 5 or so spots that are stubborn (and hard to brush from the edge of the pool).
2. How "clear" does the water need to be to stop the SLAM? Our water looks good, but is not crystal clear.

Thanks!!

 

[mknauss]

If I meet the stop criteria for SLAMing, but can still see spots of visible algae, am I ok to stop the SLAM?

Visible algae does not meet the criteria of crystal clear water. So continue the SLAM Process

 

[Beastos]

Just want to say thank you to everyone who gave advice here! Our water is algae free and crystal clear.

 

[mknauss]

Just want to say thank you to everyone who gave advice here! Our water is algae free and crystal clear.

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