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.