Something that might be able to be done is take one of those stones, drill two holes in it and wrap some wire through them. On the right side of the log, there is a branch that sticks up. Right now the rocks sit on top of it to hold it down. If I could get this to work I could loop it around the branch and bury the rock beneath the substrate and hide the wire, or whatever I use, with substrate as well. I just want to make sure that there is still some shade for the fish. Any natural ideas for that?