Looks reptile but I'm sure some soaking can turn it into an aquarium safe wood
it is held on by a stainless steel screw on bottom, I have seen a few pieces similar to this one at my LFS that are attach to slate the same wayWhat is the top piece sitting on.
Is it a piece of slate? How is it attached?
Needs to be with stainless steel screws or an aquarium safe epoxy.