top of page

Treating Yellow Algae

A Sodium Bromide product will work effectively in treating Yellow Algae in your pool. As long as the active ingredient is Sodium Bromide it will work in clearing up the algae. The percentages vary by product and the Knock Out product shown here in granular form is 99% Sodium Bromide. They also make a Knock Out Problems liquid which is about 30% Sodium Bromide and part Clarifier also but no less effective.


One thing that you need to do is to make sure you have a very high chlorine level before you start this treatment.  Bring the chlorine up to what we refer to as "Blazing High" if it is at zero ppm. This means you need to have a chlorine level of 5-10 ppm before you start using the Sodium Bromide product. If the chlorine level is already at 3-5ppm you should be okay with just the Sodium Bromide dosage and sanitizer to be added such as liquid chlorine.


One common mistake is not starting with a good chlorine level. Sodium Bromide will convert the chlorine to bromine and the Sun will also burn some off as the Bromine Molecule does not bond with the Cyanuric Acid molecule (conditioner does not protect Bromine) so even more chlorine will burn off. And some of the chlorine will be "eaten" or used up by the Yellow Algae itself. Basically, a Bromine bank is created with the active chlorine in the pool and since it is no longer protected by the Conditioner it will burn off very rapidly. Thus, you need to have plenty of chlorine in the pool, to begin with, to prevent all of it from burning off. It’s a bit complicated so just remember the higher the chlorine reading the better.


When you add any Sodium Bromide product you must follow up the application with some type of chlorine. I prefer liquid chlorine but you can use Cal-Hypo, Dichlor or other chlorine shocks. You would want to add 1 lbs. of a powder shock for every 4 oz of Sodium Bromide. The Knock Out lid is actually 2 oz. so you will need to add 2 capfuls per 10,000 gallons of water that you are treating to make 4 oz of the product.


Step One:

Bring the chlorine level up to 5-10 ppm if chlorine is zero or lower than 3 ppm.


Step Two:

Brush the affected area really well, removing as much algae as possible.


Step 3:

Add the Sodium Bromide product directly over where the algae were or are. 4 oz per 10,000 gallons of water. If in two separate spots split the dosage over each spot. If the entire pool is covered in algae you will have to quadruple the dosage. For example, if the pool is 20,000 and full of algae adding 8 gallons of liquid chlorine and 16 oz of the Sodium Bromide may be called for to be effective. You just need to multiply the amount of Sodium Bromide depending on how severe everything is in the pool.


So broadcast the Sodium Bromide over the area and then follow it with either a gallon of 12.5% liquid chlorine, 2 gallons of 6% bleach, 1 lb of Cal-Hypo or 1 lbs of Dichlor. It is crucial that you follow up the Sodium Bromide dosage with some type of chlorine to ensure the product won’t eat up the entire active chlorine in the pool. In that case, the pool will get worse and not better.

Step 4: Run pool through the entire cycle or as long as possible – 12-24 hours is optimal.



If you follow the procedure in the video below the yellow mustard algae will be destroyed and you can use a maintenance dose to prevent it from returning - about 1 oz. per 10,000 gallons. I use Sodium Bromide on my route and week to week it is the most effective way to treat algae.

buy now.jpg
bottom of page