>> No one checks your pool chemistry as carefully as YOU <<
This stuff actually works wonders on phosphates. It seems pricey, but when you realize how little you use compared to the gallons of other products you would require, it is the least expensive way to pull the phosphates out of your pool. Please use MATH so you don't waste it. It requires very little product. Get a current phosphate reading, your pool capacity, and then use the charts to determine how much product to use. Also do the other MATH . . . the filter math. If your phosphates are extremely high, do the application in multiple stages since the precipitates generated will jamb up your filter and you will have to do some filter clean outs between applications to return your pool to desirable phosphate levels.
What I consider best practice is to use a hose end liquid fertilizer spreader set to a strong mix ratio to broadcast it over the water. This keeps it from hitting the filter all at once. If you have a decent amount of phosphates there is a satisfying feeling of doing it this way. You literally will see the PR-10000 combine with the phosphates creating a "milky smoke" in the water and watch this stuff slowly fall to the bottom. IF you have a pool robot with its own internal filter, I would put it in the pool about 12-24 hours later to grab the precipitate off the bottom thereby keeping it out of your main filter so you may not have to clean it.
If your phosphates are out of control, this stuff will get them lowered and phosphates are just algae food circulating in your pool. If you are fighting with sanitizers and other algae controls all the time, check your phosphates, if they are high, this stuff will surely help knock out the phosphates and the pool algae will be easily eliminated.