He recommended building it around a tank, but she wanted the rock look inside and out. He indicated it worked for about a year and started leaking. He tried using a concrete sealer but it failed after about a month. The lady died a year later, and we ended up with it. Over the years we have tried plastering the interior and using pool paint, but it always cracked and failed. A contractor had tried fiber-glassing the interior, but as soon as the sun hit the fountain and the rock expanded, it cracked also. I saw Rubberizeit in a do-it your-self magazine, and thought I would give it a try. I blasted the inside to remove any previous materials. I used the tape on all the rock joints and most of the floor. I used two gallons of Rubberizeit, and kept coating it until you could not determine where the tape was used. I also used Rubberizeit on the top of the edge to make sure rain water would not leak down any of the top rock joints and behind the coating. Well, we filled the fountain and it has not leaked through two cycles of hot and cold weather. The pictures show the fountain after the application, and the video shows it operating. Thank you for this fantastic product. It saved me the high cost of tearing it down and having a new one built. Again Thanks, Gerald S.