To keep your water crystal clear, active carbon is the best filter media. It removes tanins from the water, which make the water tea-coloured. But carbon only provides chemical filtration: it converts certain (harmful) chemicals into less dangerous ones.
When you use carbon in your filter, you must add those ceramic tubes (or bags with bio-filtration media) as well: the benefial bacteria will live on those. And they are necessary for a healthy tank, because they are responsible for bio-filtration: those bacteria convert dangerous ammonia into nitrite (dangerous for fish as well), and other convert nitrites into nitrates (not as dangerous as the other two; nitrates are removed by doing water changes).
I use carbon (and ceramic tubes) at the moment, and they keep the water very clear and balanced. But I'm thinking of replacing the carbon with peat or blackwater extract, which add nutrients to the water and make it more tea-coloured (like many S. American rivers are).