I run dirted tanks and havn't run into persistent water clouding issues even after I have accidentally broken the cap on occaison during WC's. Carbon has cleared up any cloudiness after flooding a tank for me, so I am not sure what the issue is with amajoh's tank. Cap too thin?
newt newbie, it's not necessary to run activated carbon in a planted tank, but it can be used as a tool to address certain issues, such as excessive tannins, heavy metals, certain medications, etc. It's actually a great substrate for bacteria to grow on, as it is very porous. No issues that I am aware of with c02. The new wood is almost certainly your problem. You should be fine running carbon until it stops leeching tanins.