I used ARM before they came out with the large media but like Marc said, it was mush in a few months and my circulating pump was working like a horse to keep up with the additional head pressure created by the back pressure of the mud. I then switched over to Caribsea Florida Crushed Coral media. The media is 2-5mm and for $33 bucks, it will fill my reactor 3 times. I won't post bubble count specs since each reactor is different to achieve individual's needs. But my efllunet pH was 6.7, Alk level on the effluent was above and beyong what my salifert test kit could register. Output rate of approximately 3 drips/sec.
Unfortunately i hate testing soooooo much that I didn't test the CA level in the effluent even once in the last 6 months
Just emptied out my reactor last night after 6 months and refilled with same media and I threw in all of my acro skeletons in there at the bottom to recycle. I did have to wash the media out over and over again for about 3-5 minutes before adding it to the reactor. It had lots of fine dust and some "floaties". But I'm still on my first bag i bought at Xmas time and this will last me till next Xmas.
Did I mention how much I hate changing Ca reactor?