Carbon is fine for a reef, but if you use stuff that has alot of dust on it it can get into the tank, which is bad. Just remember, when it comes to filter media like carbon, GFO
, chemipure, whatever, that the more water you get through it and the slower it goes the better.
What size of a sump is it that you guys are running? I was looking at building one just like that for my 55. Is the water level in the fuge section high? I thought there was supposed to be a slow trickle into the fuge from section 1?