Mustard Alage????

[swampman]

We've got several yellowish/brownish areas on the white plaster walls that are concerning us. They feel "slick" to the touch, but cannot be brushed or scraped off even with alot of force. Doesn't respond to Vitamin C at all, so we suspected mustard algae. Water has always been crystal clear and no other issues at all.

We are on day 3 of SLAM and areas appear unaffected. Have brushed daily with stainless steel brush and areas are still unaffected.

First OCLT lost 1.5ppm
Second OCLT lost 2ppm
Third OCLT lost 2.5ppm

Do I continue on with SLAM, or head on over to the mustard algae SLAM level? I will attempt to post pics a little later.

 

[Texas Splash]

Welcome to TFP! There's no sense increasing to MA level yet if you can't pass the regular SLAM criteria. Odd that it feels slick to the touch and brushing doesn't effect it. Can you post a full set of water test results for us? Also confirm what product you are using to increase/maintain your FC level.

 

[swampman]

Last full test before starting SLAM
FC = 3.0
CC = 0.0
pH = 7.8
TA = 70
CH = 325
CYA = 55

Using 10% Pool Essentials bleach from Home Depot

 

[Texas Splash]

So you are now maintaining an FC of 24?

 

[swampman]

Yes, trying to

Edit: poolMath says 22 for CYA @ 55

 

[swampman]

Here is a pic. No real pattern that I can tell.

 

[Texas Splash]

Edit: poolMath says 22 for CYA @ 55

We round-up the CYA (60) which is why I mentioned 24. In your pic, hard for me to tell, but are you referring to the spots on the floor or perhaps some discoloration on the walls?

 

[swampman]

It’s the discoloration on the walls that I’m referring to

 

[Texas Splash]

It’s the discoloration on the walls that I’m referring to

That discoloration actually looks more like calcium scale or perhaps some organic staining captured within the scale. That could explain while algae treatments aren't doing anything. While your current CH isn't that high, if the pH was ever allowed to rise for an extended period of time it could happen. Do you see scale anywhere else in the pool?

 

[swampman]

My pH will creep up from time to time if I don't stay on top of it.

I am starting to see some buildup on the tile, although it is very minimal at this point.

What is the treatment for calcium scale?

 

[Texas Splash]

Scale is most commonly removed by an acid wash. Some people do a full drain (if water table allows) and wash it, while some do a no-drain acid wash. The other alternative, while not as immediate or predictable, is maintaining a lower CSI level (with consistant brushing) to help erode some of the excess scale off of the walls.