mustard algae?

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Aug 20, 2014
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Jacksonville, FL
I've been devouring the info on this site and using BBB for about a year. The site is great - thanks to everyone who makes it so. This is my 1st post.
Yesterday I discovered my Kreepy Krauly bag had turned green. I soaked it in 40% CL for 3 hours and reinstalled. I then inspected the pool and found several areas of what I believe to be mustard algae on the shaded wall of the pool.



I cleaned as best I could and raised FC to 10. I did OCLT last night and FC dropped from 8.5 to 8 overnite, 9PM to 6AM.

So: 1. does this look like mustard algae?
2. should I SLAM even though I passed OCLT?
3. if I SLAM, how long would you recommend I keep SLAMming, given that I already pass OCLT?

I have a new Stenner which I'm getting dialed in and my FC had dropped to 2 yesterday morning. I've been trying to maintain FC of 4-6

Numbers this morning:
FC 8
CC 0.5. (First time I've ever seen anything except 0)
PH 7.6
CYA 50
TA 65
CH 325

My fill source is a well with high iron.

What do you think, folks?
 
Since this is your first post: A belated welcome to TFP!

Well your description does sound a bit like mustard algae, though if your FC did drop below the minimum it does leave a little doubt. Being in shaded areas is a big red flag though.

I would bring things up to SLAM level for at least a day, brush the whole pool making especially sure to brush off any visible algae. When you pass the OCLT again then follow the Mustard Algae procedures to the letter. After that be careful not to let your FC drop below the minimum again and hopefully that will be the end of it. If you notice any problems then you will probably need to maintain a bit higher FC than you currently are, but that is a bridge that can be crossed when/if it happens.
 
Welcome to TFP! :wave:

See the Pool School article on Mustard Algae. You would start off with a regular SLAM to 20 ppm FC (for your 50 ppm CYA) and then increase the SLAM level higher to 30 ppm. You'd need to get behind lights, under removable ladders, etc. to completely eradicate the algae if it is indeed yellow/mustard. Does the algae puff up like dust when you move it? Being yellow/mustard in color and growing mostly on the shady side of the pool does sound more like yellow/mustard algae but it would be dust-like and not clumps that are a little stickier to pool surfaces.

The OCLT will only pick up larger consumption of chlorine so drops more when you have an algae bloom but doesn't drop very much if you only have limited amounts of algae. That's why the SLAM criteria also includes no longer seeing visible algae to know when you are done.
 
Thanks for the quick replies. Chemgeek, when I brush, it creates a yellow dust cloud so I think I will proceed on the assumption that it's mustard. I'll have to go in the pool to remove and brush the lights - my hair is grey and I!ll wear an old bathing suit.
I lowered the ph to 7.2 and CL is now 22. Assuming I pass OCLT tonight, I'll go to 30 ppm tomorrow for 24 hrs.

I will post progress. Thanks.
 
It's 7am and I passed OCLT - 21 to 20.5 overnight. CC is less than 0.5. As so as the sun comes up, I will remove the lights, brush everything and raise the CL to 30ppm.

Somewhere on the forum I read that one could leave the lights on the deck. Seems to me I should leave them "dangling" in the pool during the 24 hrs I'm at 30 ppm CL.
 
Bumping-up FC for 24hr MA treatment - check. :goodjob: As for the lights, normally we recommend removing and cleaning anything that "can" be removed. But if those light cannot be cleaned out of the pool, you may not have an alternative. Problem is however you don't want anything that may have algae spores on/in it to get added to what you've already accomplished by completing the SLAM. You may have to use your best judgment on that one.
 
It's been a busy day...I spent 4 hrs this morning removing the lights (no visible algae there) and brushing everything including the lights. I did find some more spots of algae on the shaded wall. I then threw all of the pool tools and toys in the pool. FC is at 30ppm this evening and tomorrow we'll start letting it drift back down and retrieve all the tools and toys.

I then checked my automated CL system and now know how my FC got so low 2 days ago when I discovered the algae. I found a tiny air leak in the suction line to my Stenner and it was delivering very little CL. Fixed that. I had checked the FC two days before and it was OK, so the algae didn't have too much time to get a foothold. (do algae have feet?)

When I retired 14 yrs ago, I thought I could relax...now I can't figure out how I had time to go to work.
 
Slam successfully completed. The pool looks great and no sign of algae.
FC 7.5
CC. 0
PH 7.4
CYA 50
TA. 65
CH. 325

I followed the instructions to the letter and it seems to have solved my MA problem. I really appreciate all the help from TFP.
 

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