So glad I took out took out the rocks and replaced them directly on the bottom in the 150 gal
tank. My other tank with a 4" sand bed also had a pile of rocks but much lower. I have a large damsel that digs holes all around the tank and tumbled over a pile of rocks against the glass. The fish moved so much sand that it looks like a valcano and a hole in the center with the bare glass showing. Had this been my large tank with big rocks it would have been a situation... Definitely put rocks on the bottom and sand around the rock not floating rock over the sand if you plan on making a very tall pile.
THANKS FOR THE ADVICE!!!! IT WAS GREAT ADVICE.