SeaKlear pool product is what I use (ordered from Amazon ~$35). The RC threads mention to use the 10 micron, but I decided to be more detailed and use a 5 micron sock. Initially, it clogs up more, but I feel that means it's doing a better job. That's just me. As far as using it as your primary use of PO4 reduction. I think there are folks that do. There was a level of deminishing returns though, meaning it doens't work that great whne phosphates are .08 and lower. There was a lot of chemistry talk to that point but it was way over my head. Lastly, there is a lot of bad info out there - Lanthanum doesn't impact sponges or clean up crew. All of them thrive in my tank. I think it's an issue if you don't use the sock.
My recommendation is if you attack PO4, you have to ensure to address NO3 as well. I have a sulfur reactor, but as with most methods in this hobby, a lot of different options to do the same thing - so I'm not saying use SeaKlear or a sulfur reactor... they both work for me - just know there are more ways to skin the cat.