Uberhoust
Fish Herder
I personally haven't had an issue. Rotting wood is part of the natural processes that occur in natural bodies of water. In the gravel will not make a big difference to the wood rot because the entire piece is under the water, the rot on the surface occurs because it is moist but still had contact with the air. Under the water the rotting occurs slower. Any leaching of impurities should be dealt with with your water changes. I change the water in my tanks every 2 weeks, with close to a 50% change, two of my tanks have a significant wood component, one of them has a piece that is 1/2 buried in aquarium soil, it has been there over a year.
As a side note where I live they have used barges to bring up logs that are up to 80 years old that sank to the bottom of the lakes near sawmills here, on the surface these logs would be unusable. The logs are still good and have been since milled for specialty products because they have a unique grain pattern.
Please remember that these are my personal experiences, and thoughts. What has worked for my might not work from you. Always monitor your fish when you do something new.
As a side note where I live they have used barges to bring up logs that are up to 80 years old that sank to the bottom of the lakes near sawmills here, on the surface these logs would be unusable. The logs are still good and have been since milled for specialty products because they have a unique grain pattern.
Please remember that these are my personal experiences, and thoughts. What has worked for my might not work from you. Always monitor your fish when you do something new.
