07-17-2011, 06:42 PM
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I took the mopani piece to work and autoclaved it (pressure steam-sterilized) it in a big pot with water at 120C for an hour (x4 times). That wood leached so much tannin that the bucket water looked like strong coffee when the sterilizing run was done. It finally got to the "tea" stage. The neat thing was the sterilization gave the entire piece a very deep, rich, brown tone. I put it into my tank and it's working great. Very minor water water discoloration that I can only tell if I drain some tank water into a white bucket. No more sap. Tank pH dropped to 6.6 from it's usual 6.8. I did have fungal growth and what looked like slime mold last week growing on the wood, but it's clearing up very nicely now and is almost gone. My BN plecos seemed to actually like the fungi stuff and the really
like the mopani wood.
Conclusion - I'd recommend large pieces of mopani wood for a tank, but only
if you have time, energy, and a big enough pot to really boil the heck out of it repeatedly! I can't imagine how dark my tank would have been from tannins without the autoclaving. If you want tannins, mopani's the way to go.