saw this on a site about carbon and reefs just need confirmation or opinions on it:
1. MAKE SURE IT IS ACTIVATED CARBON. Many types of carbon are sold in pet stores. For a reef aquarium you need carbon that has been activated--a process that substantially increases the porosity of the carbon, and as a result greatly increases the total active surface area, allowing it to be much more effective at absorbing compounds that need to be removed from the tank's water.