Mustard Algae - Bubbles?


Jan 27, 2011
I am on day 2 of shocking my pool to rid it of Mustard Algae. Prior to that my readings were as follows:

FC: 0
CC: 0
PH: 7.4
TA: 90
CH: 140
CYA: 40

I am currently maintaining shock level at 24. I woke up this morning to find bubbles forming where the water spills over from the spa. What does that mean and how do I fix that?


TFP Expert
Platinum Supporter
LifeTime Supporter
May 7, 2007
Silver Spring, MD
Organic oils from the breakdown of dead algae can sometimes cause mild foaming. This will go away as the chlorine continues to break down the oils. Various brands of algaecide will also cause foaming that goes away after about a week.


Jan 27, 2011
The only thing I've added was acid to bring the PH down since it was 8.4+ when I started. Then I used powdered shock and followed up with bleach to keep the FC levels up.

It looks like bubbles. Like you get when with blow bubbles. :D

Andrew Sarchus

Active member
Apr 11, 2011
Double check your Clorox, the "splash-less" bleach has a thickener (Cetyl betaine) that is also used elsewhere as a foaming agent. I had a somewhat similar experience in my spa and blamed the thickener.

Unfortunately I do not know how to get rid of it, I had only opened my spa when I discovered it so I just dumped the water and stopped using my wife's laundry bleach.