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. 

Sodium Bromide

Sodium Bromide works similar to an algaecide, but what it is really doing in the water is combining with free chlorine to produce chloramines. Now, normally, you don't want chloramines in your water. Also known as combined chlorine, chloramines are largely responsible for the objectionable odor of chlorine. Additionally, they are not as good at killing bacteria as chlorine is. However, chloramines are better suited to kill mustard algae than is free chlorine. 

To use sodium bromide, add an initial dose according to label instructions. At the same time, add extra chlorine. A good rule of thumb is that whenever you add  sodium bromide, add a gallon of chlorine at the same time. You need the extra chlorine so that the sodium bromide can use it to form chloramines. Continue adding a smaller maintenance dose for about a month following the initial treatment to ensure that the algae does not return. 

While sodium bromide is effective, try not to use more than recommended on the label and try not to use it for more than a month. Using too much sodium bromide will eventually make it hard for the pool to hold chlorine. 

Sodium bromide is generally packaged as Yellow Out or Yellow Treat or something like that. 

Phosphates

 Phosphates are food for algae--and any other plants

Most phosphate removers are liquids that are added to the pool water. They bind with the phosphates and the resultant slime is collected in the filter. This phosphate slime is a slimy silvery coating that causes filter pressure to climb and circulation to rapidly diminish. If using one of these types of phosphate removers, plan on cleaning your filter a couple of times shortly after adding it. 

A major pool retailer pushes a "Perfect weekly treatment" product that contains a phosphate remover. When a pool owner uses this, I am often called out to troubleshoot a poor circulation issue only to discover that this product is being used. These pool owners will often be quite adamant that  the circulation problem can't be a clogged filter because they just cleaned it. And yet, when I take apart the filter I find the tell-tale silver slime coating their grids. Once they stop using the Perfect product, their circulation problem goes away.    

There is a better way to deal with phosphates

It is called PhosLocker. It comes in a pouch that you place in your skimmer. As pool water washes over this pouch, the granules inside the pouch absorb the phosphates. You leave the pouch in the skimmer for a month to collect the phosphates. Then, and this is the cool part, you take the pouch out, cut it open and spread in your garden where the trapped phosphates fertilize your plants. After all, phosphates are plant food. So stop feeding your algae and use them to feed your plants. 

Here is a link where you can order PhosLocker.