Particularly Stubborn Mustard Algae - HELP!!

[Ricke]

23k gallon vinyl in ground chlorine pool

I started fighting an algae outbreak last year and don't have it quite dealt with yet. Picture is from last year but this year's stuff looked the same, I diagnosed it as Mustard Algae. Here is my most current state. I re-read the dealing with Mustard Algae post (which is excellent btw) and last Thursday I took out the pool light. Behind it was super nasty and there was quite a bit of the stuff there.

At that point, Thursday 6-6, my CYA was 35. Thursday through Sunday I brought my chlorine level in the morning to at least 24. I put in the max dose of an Doheny's Algaecide 60 (Poly [oxyethyline (dimethyliminio) and ethylene (dimethyliminio) ethylene dichloride]. I would re-test FC around 5pm and again around 10PM (typically adding liquid chlorine at 5pm). I scrubbed and vacuumed Thursday, Friday, Saturday and Sunday. By Saturday my water was crystal clear and remains so. I was somewhat lax on testing my other chemical levels. Friday night I measured only a 1.0 loss in FC, Saturday day I had about a 10PPM loss in FC. Saturday night I measured a .5 loss in FC and Sunday day I measured a at least a 12PPM loss in FC (I added 4 gallons of 12.5% liquid chlorine Sunday, two at 10 am and two more at 6pm).

I started more a more precise journal Sunday evening here are my measurements. Today was a 14PPm FC loss during the day and ZERO at night!!! HELP!! I know daylight can eat FC but at 35 CYA 14PPM loss is not normal. Is it even possible that it's the Algaecide? I've been measuring a +6 or so FC loss during the day since I opened my pool on May 18th. I've been more or less at SLAM levels in my pool since I opened it (I've been pretty lax with it though until Thursday 6-6).

Day	Time	FC	CC	CYA	PH	Alk	CH
6-9	17:00	24	0.5		7.4
6-10	6:00	24	0
6-10	18:00	10	0	35	7.2	90	200?

 

[Newdude]

Everything is exactly as it should be. Mustard algae SLAM FC is nearly impossible to maintain. (Your 24 FC, 60% of 40 CYA).

But at night, very little loss. FC burns off as a % and somewhere near 20 it becomes really noticeable and gets worse the higher you go.

That's why we perform a regulat slam to kill everything and everything, then go to MA slam after, and only for 24 hours.

Well done. Pass tonight's OCLT and put this one in the books. You want 1 FC or less loss and .5 CC or less along with clear water.

 

[proavia]

You need to perform a proper SLAM Process.
Adding algaecide is not part of that.
The algaecide will use some FC.

You need to complete a SLAM Process first - meeting all 3 exit criteria - and then increase FC to the mustard algae levels for 24 hours.

CYA of 35 gets rounded up to 40.

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[Ricke]

You need to perform a proper SLAM Process.
Adding algaecide is not part of that.
The algaecide will use some FC.

You need to complete a SLAM Process first - meeting all 3 exit criteria - and then increase FC to the mustard algae levels for 24 hours.

CYA of 35 gets rounded up to 40.

Use PoolMath to enter your test results and share your PoolMath logs to your forum account so we all can see them.

What test kit are you using?
Fill out your signature with pool, pool equipment (including manufacturers and model numbers) and test kit info.
This assists us in providing you help without needing to ask you each time for this important information.

https://www.troublefreepool.com/account/signature

Thanks! I got everything in my signature but the pool equipment I'll have to read the fine print on my gear.

 

[Ricke]

Everything is exactly as it should be. Mustard algae SLAM FC is nearly impossible to maintain. (Your 24 FC, 60% of 40 CYA).

But at night, very little loss. FC burns off as a % and somewhere near 20 it becomes really noticeable and gets worse the higher you go.

That's why we perform a regulat slam to kill everything and everything, then go to MA slam after, and only for 24 hours.

Well done. Pass tonight's OCLT and put this one in the books. You want 1 FC or less loss and .5 CC or less along with clear water.

Thanks newdude!!! I think what you're saying is that at 35 CYA a 24 FC is not sustainable and will burn off rapidly. So once I get back down to a normal level more like 6 I should see, what, maybe 1-2 FC loss per day?

 

[Newdude]

35 CYA a 24 FC

Round up to the next 10 for CYA. Yours is a 40. (31-39=40). And you're at 60% which is mustard algae SLAM level, to be done when needed *after passing regular slam* @ 40% CYA.

Have a refresher
SLAM Process

You need no visible alage whatsoever
OCLT 1 or less
CC .5 or less

Then go to MA slam for 24 hours. (Because the loss seen will be stoopid high, like you saw).

After that, let FC drift down to regular target range and you should see appropriate loss for this point in the season.

 

[Ricke]

Update. I’m giving up and seeking professional help. I’ve done the super duper mustard slam process twice now and done hour after hour after hour of scrubbing day after day. And it’s back again.

 

[Ricke]

Update. I’m giving up and seeking professional help. I’ve done the super duper mustard slam process twice now and done hour after hour after hour of scrubbing day after day. And it’s back again.

What is impressive is that 48hrs ago I had crystal clear water, put in a gallon of bleach to get my FC above 10 at 30cya. I covered it to go out of town and came back to this!! FC still at 9 and CC at .5