Just woundering.  For those of us that are using a cal reactor.  What kind of media are you using.  Reason I am asking is I ordered the ARM media, and then did some research and found that some people have had PO4 issuse with this media.

It depends on which reactor you have. Some can only run the larger Schuran or Gen-X type media while others prefer that you run Rowalith, Ca-Pur, dolomite/aragonite mix or ARM media. To an extent, they will all have some level of phosphate in them.