Algaecides and Mustard Algae

 Chlorine will kill most algae, but has a hard time killing mustard algae. Mustard algae is a yellow algae that will grow on the sides of a pool. It generally brushes off easily, but if you don't kill it, it will come back. 

In addition to showing up in the pool, it will also coat the grid inside the filter and cause the filter pressure to build up quickly (sometimes within a day after cleaning). 

The only way to deal with mustard algae is to kill it with one of the following types of algaecide:

• Copper based algaecide -- this is my first weapon of choice for mustard algae. You can buy it as a liquid or in a more easy to use canister form (Pool Rx). 
• Silver algaecide -- this is another good tool for killing mustard algae.
• Sodium Bromide -- this also works to kill black algae by turning free chlorine into chloramines. While this is not normally a good idea, it works for mustard algae.

Each of these is further explained in other posts on this same blog. Look there for further information and be sure to follow package labels for dosing amounts. 

With all of these, brushing is essential. As long as the algae is on the side of the pool, it is somewhat protected from the chemicals in the water. Brush daily to put the algae in the water so that the chlorine and algaecide can kill it.

Finally, if you have mustard algae, you will need to clean your filter often until you kill the algae--and then once after you do kill the algae to remove the dead algae from the filter. As long as there is algae in the pool, your filter pressure will go up and your circulation will be poor. Kill it first, then filter out the dead algae.   

P.S. If treating mustard algae don't bother using an Algae Preventative (it is much too late to use a preventative once you already have it). Also polymer algaecides like algaecide 60, while good for green algae are not going to work for mustard algae.