Anyone using Zeo rocks?

[MikeP]

I bought a bag of these a little while ago. They came with no instructions and I can't seem to find any useful info on-line. So how do I use them properly? I can put some in one of my phosban reactors (but then I have to give up either carbon or GFO). Could I put them in a high flow area of the sump? Also how much do I use and how often should they be changed out?

Thanks