Agree on the prep work for Liners I have a 1000 gallon Koi pond in my greenhouse that I used a liner. I used old shingles and the then cotton batting to get a smooth surface. I got my liner from Bend Tarp and Liner it ran about 30 cents a square foot and has a 20 year guarantee and they will make it to the size you want. They have good information on site prep on their website so you might do a search for them and look at the information. Bob