What to place under preformed pond liner?

Hello,
I just got a 100 gallon preformed pond liner, I will try to bury it only half way. But I was wondering if I had to place anything under it. I bought it from a Craigslist listing and teh guy did not know much. I heard is a good idea to put a kind of cushioning between the earth and the liner. I have no idea if that is so. Any suggestions are welcome.
Thanks
~Dulci

Hey Dulci- People have been known to put recycled old carpet, 2" sand, or newspaper to pad pond liners. I don't know that I've heard of anyone padding a plastic pre-formed liner though, but I could be wrong and I can't believe that it would be a bad thing if you did! Good score on craigslist (my favorite) !!

Thanks art!

Tell me about it, I love craigslist. I've found most of my garden stuff there all you have to do is keep an eye open for stuff you are looking for and not grow desperate and hit the store. I was waiting for a listing about a preformed liner all winter. And this Sunday BINGO!.

I will try to put an old blanketI guess. Maybe what I heard was about the flexible liners. Either way I can't wait to start putting it together.

Dulci...you really need to put sand under the preformed pond. No matter how hard you
try to level off the dirt in the hole you dug, it won't be level. So use some sand and level that off. Then put sand down the sides too. But it really should be dug in more than half way. That will keep the pond from 'bowing' on the sides when the ice forms in the winter.
Have fun ponding!

4brugs thank you too. See? That's what I didnt want, to start doing this without any guidance. So your advice is much appreciated.
~Dulci

If you plan on leaving it in over winter without a deicer dig it in all the way.

sand, sand, sand, builders sand, play sand, any sand - sand
Where preformeds fail most often is a crack in the lip of the top edge because of lack of support underneath the lip. Rain can wash away the dirt over time from any gap around the sides or down the sides to any gap on the bottom. If you use sand you can add some at any time in the future to keep the sides, lip and bottom fully supported.

If not fully buried distortion from freezing and thawing will eventually cause fatigue cracks.

I have had my pond for about 8 years and have had no problems. I used sand to level everything and then bought some cheap blankets at good will. It has remained stable, with no shifting or cracking since.

Thank you so much for all the info. I decided to follow your advise and dig. LOL
Let me tell you is not an easy task to dig in my yard, there are some kind of thin roots all over that part of the yard; so is extra work to break through all of them. I also had to go and buy sand. But when i was done and placed the liner I thought all that work was worth it. I will take a pic once i get home to show you.

Dulci, waiting for that picture. You'll be glad you dug it all the way in being in zone 6.