Every year when I trim my trees, I put them in concrete and sink them. I usually have 5 or 6 , 2 go to my ''main'' locations to keep them renewed and the others I use to start a new location that I have found and think will make a good spot. Not sure on the rotting question although it makes sense. I have enough limbs each year that I figure I have a pretty good pile going on by now and the fish are there!! That's the main thing...