Some people do others don't I didn't and should have. I thought all was well when I first filled my 120 like 7 years ago and there must have been a slight crown in the granite slab I had the tank on and two days after filling the beast was watching tv, sitting right next to the tank it was like somebody fired a gun right next to my head, the laminated edge detail on the countertop cracked, needless to say it scared the hell out of me. Also my tank has always had about 1/16" gap in the center along the front edge and it has always worried me a little so having said all this I think I would foam my next one lol.