Using PhosFree for algae control

[PoolDoc]

I think you'd be better off saving it.

Go ahead and test your FILL water. Then we can figure out how to dose your pool to compensate for water additions, ie, 1" of added water = X oz of phosphate remover.

Also, Phos-Free is one of the more expensive ways to remove phosphates. Currently the Kem-Tek product (link below) seems to be the lowest cost ($'s/ppm PO4 removed) product. So, if you have Phos-Free already, don't throw it away. But, don't buy more, either since it costs a significantly more than the Kem-Tek product does.

Regarding other sources, as long as you use unblended chemicals (which we recommend) and avoid pool 'steroids and vitamins' -- products from United Chemical, Jacks Magic, SeaKlear, Natural Chemistry, etc -- and aren't having to deal with metals in your pool, you shouldn't be adding any phosphates, except via your fill water.

[ Links to products previously listed here removed!]
Phosphate removers vary greatly in quality. By far the best choice is Orenda's PR10000 removing 10,000 ppb (10 ppm) from 10,000 gallons of water. I've recommended other products in the past, only to discover they were playing games with the concentration!

Orenda PR10000 Phosphate Remover @ Amazon