I was given a pond for Fathers day and am getting ready to install it. I think it is 60 gallon bean shape. When it was bought the salesman made a comment to my wife about most people end up with their pond cracking in the winter. He said you should put sand around it. I assumed this was for expansion. Is it necessary? I am not sure what type of material the pond is made from but it is some what flexible. I live south eastern PA and because of wind it can get somewhat cold at my home. The pond is 2 or 3 foot from the house if that matters and 6 foot from the septic tank so I figured that the ground that close would not get as cold as the rest of the yard.