yeah i think some of it is influenced by the color of the wood from my experience the wood with the lighter coloring leaks more tannins.. you boiled it for 8 hrs? and soaked it and it still turned your water brown? did you change the water frequently when boiling.. i changed mine about every 30 min or less.. regardless the tannins are not harmful to the fish.. and with a decent amount of carbon like the amnt for aqua clear not that aqueon cartridge junk it should not discolor it terribly just change the carbon once to twice a month and frequent water changes and over time the tannin release will be minimal in my experience..