That is a beautiful tank, and I love Geophagus, having had a couple many years ago. When I had them they dug up the whole substrate repeatedly, then bred. Watching them herd their fry, sucking them into their mouths when I would get too close, was fascinating. Of course I knew next to nothing about proper care of either fish or plants back then so the fish died within a year or so. And, I vote to keep the stump!