The passive method works OK, this is purely anecdotal so take it with a gran of sand, but IME carbon long term in a tank can be detrimental. I much prefer to use it short term to polish water, it can get exhausted quickly.
Most of the lfs I talk to said, at first it gets exhausted quickly, so your first batch should be in there for about a week. Then after that you keep the following batches in for the month or w/e.