I have this tannin problem in my new tank due to corkbark and driftwood. I have to run activated carbon in my Fluval 305 to combat it. My question is - what are the "good" things in my water that carbon removes and how can I replenish them? It looks like I'll have to run carbon filtration for a long time until my water clears to a level I can live with. Thanks for replies :coffee: