About 5 years ago I cut down a large(make that huge) cedar tree and drug it, with my tractor, and a long heavy rope into the water next to the dam. After a couple of good rains it was submerged and working like a champ. But, it never collected any algae. Then some heavy winds came and the darn thing floated to the other end of the pond. It stopped and hung up in some shallows of my favorite fishing spot. So, I got my jon boat and tied onto it to drag it back. No way. I had to let out all of the rope and manually drag it.
I was wishing I had used some weighted plastic.
I've used both and find advantages and disadvantages to both.
Placed strategically along fish travel routes, as Bob said, I prefer plastics. For something placed along the bank, into the water, I prefer natural. But then, my water levels vary a lot during the summer.
