More mustard algae - need help with diagnosis

[HO249]

Hello,

This is my first post, and I'm hoping you folks can help me identify the algae infestation in our pool. First, here are my test results from today:

FC = 4.5
CC = 0.5
TC = 5.0

CH = 475
TA = 110
pH = 7.8
CYA = 50

I'm pretty sure the problem here is algae; I determined this using a 3" chlorine puck in a sock on the pool surface - it cleaned up the algae beneath it.
I also tried the vitamin C rub, and it had no effect (I took the rest of the tabs, they seemed to have no effect either).

I uploaded 2 pictures, which I took today. The sky was overcast, so the mottled stains are dark. In bright sunlight, they are yellowish in color. I used a zoom for the bottom picture.

I'd appreciate any diagnosis information and advice. Thanks!

 

[kimkats]

Hi! That is neat the puck cleaned it up! We can help you get the whole thing cleaned up I bet!

So a couple of questions for you. Ready?

-How did you get those test results?

-Does the algae "puff up" when brushed?

These will get us started down the path to a clear pool for you!

Kim :cat:

 

[HO249]

Hi Kim,

Wow, that was quick! To answer your questions: I used my trusty TF-100 test kit and speed stirrer for the tests. The algae does not puff up when brushed; in fact, it's on the plaster very solidly.

Thanks!

 

[Texas Splash]

There's a chance it might be related to scaling. I ran your numbers on the Poolmath Calculator, and your CSI is currently at .56 - right at the top-end for plaster scale. If that has been allowed to stay that way for a while, it's very possible. Is there any of those discolorations above the water line where you can apply some acid directly to it? It may bubble, if it does it's another indication of scale. While algae can certainly be stubborn, you should be able to scrub/scratch it a bit unless it's stained into to the plaster.

If you're not losing FC a lot each day, it may not be algae. But you should still do an overnight (OCLT) test to confirm. If you find that you are losing FC too fast each day (more than 4 ppm per day), you might need to SLAM first, then keep the FC slightly elevated for a while to see if it helps. Otherwise, if it's calcium scale, you may need to simply lower pH a little more consistently, hope for more of our local rain to help with CH water exchange, and try to keep the CSI (Calcium Saturation Index) level more towards the slightly negative side of zero for a while to help that scale try to dissipate. You'll see the CSI row on the Poolmath Calculator once you enter all of your normal test results.

If that seems like "info overload", please let us know and we'll try to explain further. I don't want it to seem overwhelming.

 

[kimkats]

Sweet on the good test kit! Nice pick! Can you please add that to your siggy so everyone will know as that is the corner stone to TFP.

So that is NOT mustard algae. Mustard algae goes away when brushed. I would go with what Pat ^^^ said. Let us know what you find out following his suggestion on the OCLT Pool School - Perform the Overnight FC Loss Test (OCLT)

Kim:cat:

 

[cowboycasey]

Welcome to TFP, you're off to a great start Poolmath is a friend to all of us here, makes life much easier...

 

[duraleigh]

I believe your issue is a combination of scaling where the calcium deposits have encapsulated so algae or possible a type of algae is growing within.

In either case, you have to get rid of that scaling.

The best solution is a professional acid wash but you will need to drain your pool. Others have had good success with a no-drain acid wash treatment.

Both treatments are not for the faint-hearted so if you are at all hesitant, pay someone to do it.

Once you scaling issue is solved, manage your pH down in the lower 7's and you probably won't see scaling again.