Yes that was what I was thinking. It sounds like the entire floor is flexing so probably nothing else you can do. I doubt it will hurt the tank . My floors have alway had some type of movment. I had two 180 gallon tanks and one 150 gallon on the first floor over a basement all within 10 feet of each other and never had a failure and they were up for years. The only tank that is totally rock solid is my 125 gallon sump sitting on concrete in the basement.