Originally Posted by mr_X
Your rock should have been placed before your sand. I would correct that if you can. It would be a shame to have a rock slide that kills the EG or something else.
I agree with Mr X. Your rocks should be placed on the glass bottom or even better a piece of egg crate on the bottom. During the next water change I'd pull the rocks out and put them in the old water, push/work a piece of egg crate through the sand to the bottom under where the rock sits then put the rock back in and work it down to the crate. With the big rocks you appear to have it should be relatively simple.
Otherwise one day there will be a rock shift.