Like alex said the tannins are natural and alright. If you want to get rid of them, just do a water change. Oh, did you boil your driftwood before putting it in? Typically that is the best way to get out the tannins before it goes into a tank.
I let it soak for about 36 hours. I didn't have anything suitable to boil it in though, but I did pour boiling water over it before I put it in. I was aware it was harmless, but I did hear it lowers PH.
Funnily enough, the little fella for the first time has gone crazy building bubble nests! There are about 3 small ones. He must really love the murky water