I found a video which says your diamond goby can also be a total jerk.
This is a total A Hole move... funny but real A Hole...
I am so glad I do not have two of them. mine is a pain covering everything in sand all the time. when he wants me to feed him, he looks at me through the glass, swims down into his burrow, scoops up a mouthful of sand, then spits it at the glass. if I don't respond, he does it again but swims to the wave maker and spits it in there covering the whole scape. he knows when the wave turns off, food gets added.