Planted Tank Guru
Join Date: Nov 2009
Location: Missouri united states
Carbon,no more than is found in most cartridges is only effective for a couple week's.
After that, it is just one more surface for beneficial bacteria to colonize upon.
Is not needed in planted tank,but won't hurt nothin either assuming you feed the plant's regularly.
Would leave it for now,and replace it with foam after a couple week's.