http://www.canreef.com/vbulletin/showthread.php?t=21978
The phosphate reactors I've seen are basically just an upweller system whereby water is forced through a small column in the middle of a larger tube and expelled through the bottom into the main tube which contains the phosphate remover and then flows upwards through the media and out the top. IMO they're much more efficient than placing a bag of phosphate remover in a high flow area as greater flow reaches more surface area of the phosphate remover. Seems that way to me anyways, I've had more success with the reactor than just putting a bag of it in my sump. It kicks ass for carbon as well.