There are 2 "main" products phosban and rowa-phos (or kent's version of PowerPhos or something like that), the later is more expensive, both work rather well and I think are "the product to use" as neither leeches back into the system once they are "used". I've used both, I'm using phosban now (first time trying), put it in my reactor, and the issue with it is it's much more dense, so the pump is having a really hard time pushing against it, so I'm not too keen on that, although phosban is cheaper per amount of PO4 removed.