The best insulation for a pond must go in place during installation, but you can still add some insulation to an existing pond. Insulation can keep fish and plants alive in cold climates where water still rarely freezes over entirely. If you struggle with a lot of ice development or temperatures below 0 F in the winter, you’ll likely need heaters in addition to the insulation. Buried or surface insulation definitely makes heating the pond more efficient and less expensive over the winter.
Efficient insulation is applied as expanding foam between the soil and the underlayment or liner. Spread at least six inches of foam over the entire excavated pond opening to prepare a thermal barrier to stabilize water temperatures. Digging a deeper pond can accomplish the same function without requiring foam at the bottom. If you have an existing pond and won’t be replacing the liner for years still, try setting up foam panels that extend over part of the surface of the water. Leave the center of the pond exposed and break any ice that forms there so that the fish can continue getting a fresh supply of oxygen while aerators are turned off.
