I've seen recommendations here to use phosban and/or phosban reactor, but really you should find out why you have high phosphates.
For me, I was feeding twice a day, which turned out to be way more than my fish actually needed. Once I went down to once a day, my phosphates and nitrates dropped by half. I tried phosban in my canister filter once before I changed the feeding pattern, but it didn't work for me, the feeding was my problem. I have no experience with the reactor.