Mustard Algae Slam - but no FAS-DPD test available

[AlanH]

Hopefully I can get some thoughts about slamming a budding mustard algae bloom in my pool. The hurdle is that I live in Nicaragua and there is no way I can do (or buy) a FAS-DPD test.

The best I have is Pentair's Pro 11 test kit. It uses tablets to test for free chlorine (DPD1) and, using that sample, adding another tablet for total chlorine (DPD3) - subtracting free from total to get combined, if any.

The instructions say that if the color darkens chloramines are present. To my eye I do not see any darkening. Another issue with this kit is that it states if there is more than a 0.2ppm increase a slam may be required. The comparator only has markings for 0.5, 1.0, 1.5, 2.0, 5.0, & 10.0. How do you measure 0.2 on that scale? And chlorine (bleach) levels in the 16+ range for slamming?

Can I dilute samples of the pool water while slamming to work within the range of the kit that I have? I recall a thread about dilution and measuring the concentration of bleach in jugs (to verify that x% was indeed x%). Would that be a work-around?

Pool numbers as best as this kit reports them (pre-slam):
FC - 5+ish
TC - 5+ish
CC - 0
pH - 7.8
TA - 90
WH - 300
CYA - 35-40

Thanks for your thoughts and recommendations.

 

[mknauss]

The best you can do is cut the pool water with distilled water (not tap water) to get the FC level into the range your equipment can read. I would suggest overshooting the FC level as your test will be approximate, at best.

 

[AlanH]

Moved from here.
Just keeping an eye on this forum as I deal with my algae bloom. Wouldn't FC depend on type of algae? Don't know for the OP but in my case Pool Math recommends FC=22 for the mustard algae I have, versus FC=14 for a "regular" shock. (13000 gal, CYA=35ish).

 

[AlanH]

Thanks. That seems to be working for levels of FC=22ish for mustard algae (as recommended by Pool Math) and dilutions of 4-5 to 1. Getting down to CC of 0.5 or lower and OCLT of a loss of 1.0 ppm or less may be a challenge. The best (finest scale) comparator I have is one left over from a K-1000 kit. Is there any accuracy at all in dilutions of 10-20 to 1?

 

[ajw22]

Just keeping an eye on this forum as I deal with my algae bloom. Wouldn't FC depend on type of algae? Don't know for the OP but in my case Pool Math recommends FC=22 for the mustard algae I have, versus FC=14 for a "regular" shock. (13000 gal, CYA=35ish).

What makes you think you have mustard algae?

And if you have it you first do a complete SLAM then raise to MA FC for 24 hours.

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

 

[red-beard]

Can you attach the picture using the "attach files" below? I'd like to see a closer view of that algae.

 

[AlanH]

@ajw22 - the algae has definite yellow color. On the rare occasion I have had to deal with a green algae but this is very visibly different. Are you saying that for mustard algae do a "normal" SLAM first, which for me would be FC=14 (CYA=35), followed by a higher concentration SLAM (FC=22) for 24 hours. I didn't pick that up from the SLAM info blog; was just going by what Pool Math said.

@red-beard - close up of original photo. No other photos available as condition has improved substantially over the last 48 hours. Black stuff is leaf stems and fine leaves.

 

[red-beard]

The good news, that looks like Green Algae. Mustard is usually in a shadow area and looks more like a coating than streaks. And not so much yellow, as light brown. Or at least that was the way it showed up in my pool. I fought that beast for YEARS!

You want to keep at the regular SLAM level until you pass the OCLT, then you run it up to the Mustard Algae level to stake it in the heart.

If it really is M.A., you may wish to keep your Free Chlorine level a bit higher than normal. With my SWG and my CYA at 70, I keep my FC around 10 ppm, to make sure the Mustard Algae does not come back.

Last year, as I was working on my Polaris 280, I found algae under the hose nuts. It lurks in the cavity behind the lights. While the pool is a SLAM levels, you want to get into those areas and clean!

 

[red-beard]

This is what a Bad Mustard attack looks like.

 

[ajw22]

@ajw22 - the algae has definite yellow color. On the rare occasion I have had to deal with a green algae but this is very visibly different. Are you saying that for mustard algae do a "normal" SLAM first, which for me would be FC=14 (CYA=35), followed by a higher concentration SLAM (FC=22) for 24 hours. I didn't pick that up from the SLAM info blog; was just going by what Pool Math said.

There is an article in Pool School about each of the types of algae...

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

 

[AlanH]

Thanks all. @red-beard - great if it is green algae (well, better). I think it would be best to treat as mustard though. The photo is not typical of what I saw in the pool. That streak is a peculiarity of my circulation that creates an eddy in that area and anything that is in the pool always shows up there swirling/streaking. What you were saying about a coating in shady areas is more like what there was in the deep more shaded end. The day I took the photo there was a strong wind and wavelets on the surface obscured the larger blotches in that part of the pool making any photo of that part a blurred mess. At the moment the pool looks great and is crystal clear (has been slammed for about 48 hours at a mustard slam level).

I know the OCLT calls for a FAS-DPD test but as I said in my OP I do not have (and cannot buy) that test. What I do have is Pentair's Pro-11 kit that uses DPD#1 tablets to test for free chlorine and DPD#3 tablets for total chlorine (subtracting free from total to get combined). The comparator has marking of 0.5, 1.0, 1.5 & 2.0 on the low end of the scale (using a pink to red color gradient). The most visible difference is between 1.0 and 2.0.

Any thoughts/experience that, through dilution, if I can produce a reading of 2.0 after sunset, and repeat the measure before sunrise, and the reading is not less than 1.0, can I even somewhat reliably count on such a result to replicate a OCLT?

 

[red-beard]

Well, you do what you have to do on making your tests work. Diluting will work, but use distilled water or previously boiled water to make sure it does not have chlorine in it.

 

[AlanH]

Just a follow-up. I was able to dilute the water samples and use the DPD tablets using the 0.5 markings on the lower end of the comparator. I used the OTO drops first (with dilution) to get a ball park of the dilutuion required since the tablets are somewhat expensive and hard to find. After the final 24 hour mustard algae slam the OCLT showed no chlorine loss/change, CC was practically 0, and the pool has been sparkling clear for the last week.

 

[red-beard]

Fantastic!