Sodium Bromide to combat Mustard algae in SWG pool

Jun 10, 2008
First off, great forum. been lurking for a while.

Got a problem with Mustard Algea.

28000 gallon painted plaster pool

Intelliclhor IC40. Sand filter.

TA 76
CH 200
CYA 45
Borates 35
PH 7.6-7.8
FC 3-5 ppm
Salt 3400

Water is crystal clear, but I Mustard algae growing on the steps if I don't brush them often or if the FC drops down to 1 or 2 ppm

I noticed most treatment for Mustard algae is Sodium Bromide. I guessing my SWG will split this into bromide.

Think if I put a lot in this could cure my problem?
Not all SWGs are compatible with sodium bromide. Some cells can be ruined by it so consult your owners manual before adding it!


TFP Expert
Apr 16, 2007
Ft Lauderdale, Florida
The Sodium Bromide is used in conjunction with several shock treatments to activate it. Sodium bromide is bromine salt. By itself, it does nothing. Adding the shock dose, or having the SCG continually generate chlorine, will eventually reactivate the bromine salt.
The problem is that the resulting bromine (instead of chlorine) will not be sufficient to maintain a safe residual, since there is not enough of a sodium bromide bank to generate enough sanitizer.

The treatment will rid the mustard algae very well. The pool will look great for about 2 weeks, your chlorine residual (which will actually be converting to a bromine residual) will drop off, then the algae will come back.
It's not that the sodium bromide will react with the salt blades to damage it. It's the fact that you're not going to be able to get a safe residual, where the first reaction is to increase the SCG output. That's where the problem occurs. The higher output will result in shorter cell life.

You can use this treatment, but you will have to turn OFF the SCG, for about a two week period. Do the Mustard Algae treatment, but continue to maintain shock dosages until you see the chlorine residual being maintained without having to add more chlorine.

Better yet, as frustratedpoolmom is suggesting, just use plain ole bleach to get rid of it.

Shock, brush, vaccum to waste.
Jun 10, 2008

Well, i added about 8 oz today. :oops: I can't find anything about it one way or the other on the net or owners manual.

Only cautions i see-

Don't fertilizer
Never use dry acid
Don't add chemicals with cell on
Don't let stabilizer drop below 50 ppm :oops:

With Sodium Bromide being a common chemical, looks like they would put a caution. I gotta believe a small amount is not going to hurt.


TFP Expert
Apr 16, 2007
Ft Lauderdale, Florida
It may or may not. Just remember to keep an eye on your sanitizer level and if you find it dropping and not being able to be maintained, turn your SCG OFF, and hand treat with shock doses of chlorine to maintain a safe residual.


TFP Expert
Platinum Supporter
LifeTime Supporter
May 7, 2007
Silver Spring, MD
Sodium bromide is part of the bromine based sanitation family, sometimes used instead of chlorine, particularly in spa's. The version used for bromine systems is slightly different and sticks around for a long time. But for chlorine pool use it is in a comparatively unstable form that breaks down and goes away after a while. FC turns it into bromine, which kills algae.

The main use of sodium bromide is to get around very high CYA levels. Sodium bromide is not affected by CYA, so it will work at reasonable doses even when chlorine requires huge doses because of high CYA levels. The problem is that FC activates bromine and goes away and bromine is not stable in sunlight and deactivates. So you have a tricky transition until the sodium bromide breaks down, when you can't hold a FC level. That creates enough problems that it is rarely worth using.

A few SWG systems are designed to work with bromine systems and are fine with sodium bromide, but many SWGs can suffer cell plate damage from sodium bromide.
Jun 10, 2008
so the small amount I added should break down?

I was reading and in spa the sodium bromide levels are much higher. I figure i have about 2.5 ppm and spa's run 3000 ppm if I read correct.

Thanks for the help. :-D