it really does come down to what you are stocking and how heavy of a bio-load you are carrying.
Carbon should only be used in a canister type filter or some means where it is stationary but water can flow through it.
Carbon should NEVER be used in a media reactor as the action of the carbon moving around will cause it to break up and bits will make their way into the display.
Micro particles of carbon are one suspected cause of HLLE
Purigen, bio-pellets, and phosphate removers work in reactors because they do not degrade and break up.
(granulated ferrous oxide) is used in reactors, but the flow is very slow so the granules do not mash around and break up.
A inexpensive canister filter pulling/returning from the sump will suffice to use any type of chemical media.