Corleone
Fish Herder
Sometimes it can take a while for wood to stop leaching tannins, especially a big piece. I treated two pieces with boiling water every day for two weeks and soaked them in between, and they still turned my water a dull brown. They've been in for two months and if I look at a sheet of white paper through the tank, I can still see the color a bit. It's harmless to fish, and some like it.