I agree not to get something too fine. I got the coralife media, and it is particularly fine. I get a lot of gunk caught up in it and I have to clean it out periodically (more than I should). I would not buy the coralife again.
Someone suggested putting a stronger circulation pump in there, I put in a RIO 2100, and it helped for a while, but it still gets all clogged up. I feel if there were bigger spaces between the bits of reactor media this would not happen so badly.
Well, I was a strong advocate of crushed coral because it was very cheap, could be rinsed out fairly easily prior to use, and dissolved very easily at pH of 6.7-6.8. I also grew to hate the living heck out of it because the PO4 released caused bullet and nuclear proof algae (bryopsis) to grow. That was a battle I wouldn't wish on anyone.
I came across the Schuran media, which claims no PO4 release at all. How accurate that is remains to be shown. It does require a much lower pH to dissolve (6.2-6.5), but it will not turn into mush regardless of how low you run the pH. That in itself is a huge plus that none of the other media have. If the lack of PO4 is correct, then we have found the first jackpot in Aquarium equipment/supplement since synthetic salt
Premium Aquatics and Aquatic Ecosystems carry it at $4/Kg or close that that.