I have a plastic pond 6x4x2. My husband, master carpenter, framed it like a house wall. Used styrofoam for insulation for floor and walls. He used 2x4's and plywood. I left an open area to allow for equipment and air circulation around the pond. My fish like to splash when the glass lid is open. Caulk the inside of your frame. I learned the hardway when I had filter leak. I also live in Ontario. There is a company around the Newmarket area that will create a plastic pond to any size you wish. Big $$$$ for that. My pond houses 2 ID Sharks 25" and 17" and a 22" Golden Clown Knife. One of my sharks is over 15 years old. Other than not getting a side view it was the best thing I could do for my fish. It's not finished yet. and it's a little dirty. I hurt my arm and can't do anything but feed them right now.