Well I'm playing the part of the Guinea Pig. I'm running 1/2 Cup of Media, or .196 lbs. Only about 1-1/4" high in the Reactor. They should make a style of Reactors 1/2 Height.
I'm running it with a MJ1200 with a valve almost fully closed.
The media has a lot more "fines" in it than Phosban. I never used Rowaphos before. I ran it in the sink for a good 10 minutes, a very fine reddish brown rust could be seen on my sink bottom. A very small amount of material but you dont want it in your tank. I say it's reddish brown, but the actual media is jet black.
In the reactor the media looks just like phosban, I've got it floating up just enough to see it move. I plan to run it only for a couple hours tonight, then start it back up tomorrow.