No issues with Cedar, in fact, I think they are the most commonly used tree due to low tannins and their longevity underwater. MisterA, I think Dave came up with a bucket test you can do, if you're ever unsure about a particular tree you want to toss in for structure. Just cut some small branches up, bark, leaves, whatever, and add them to a bucket of water. If you don't see a color change, you're probably good to go. You can also toss in a fish to see if it dies in the tree-infused water. But Cedar is safe, either way. I'd stay away from Oak.
