Slightly off topic said:I would use them as directed on the packaging.
Awesome said:Try looking for a report by Richard Harker.
http://www.fishchannel.com/saltwater-aquariums/aquarium-frontiers/reef-aquarium-granular-activated-carbon.aspx
http://www.fishchannel.com/saltwater-aquariums/aquarium-frontiers/reef-aquarium-granular-activated-carbon-2.aspx