That's a problem.
You need to make sure it's really clean and that there aren't parasites inside. They can go dormant and come out later.
( that's what I've been told).
Invest in a good UV.
My first piece I found in a river had a bad bacteria on it. Wasn't there when I put it in my tank, but 3 weeks later ,my rays stopped eating, and then I noticed the slime on the driftwood.
I pulled the wood out and the next day they were eating just fine.
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