[Dentoid]

It removes the yellowing compounds from the water and in essence "polishes" the water. That is why they say be careful using carbon and changing carbon with coral because the removal of the yellowing compounds can have a profound effect on how much light reaches the coral.

Terry, I guess it depends on how dirty the water is and how quickly the detritus builds up in the pores of the carbon. Once the pores of the carbon are obstructed, whether it's from detritus, bacteria or the chemicals it's used to remove, it's not going to absorb anything else. Sure you can rinse it and leave it in there for a month or two, but its effectiveness is lost.