I recently put a load of bogwood in my tank, and despite washing it for several days it still leeched quite heavily into the water. I've been told that adding carbon to the filter will help quickly remove the tannin, BUT, will it harm my Apple and Malaysian Trumpet snails in any way as if there is any risk to them from it I would rather put up with the cloudy water as I love them as much as I love the Barbs in there.....