Rigid fish pond shells make an excellent alternative to flexible pond liners, especially in areas where soft soil may settle and erode over time, altering the desired shape of your pond. These preformed ponds come in a variety of styles but are extremely limiting when it comes to making large, custom ponds. One option to build a better pond is to put two rigid fish ponds together to create a larger one.
Determine the orientation of the final fish pond by moving the two rigid shells around until you achieve the desired positioning. It is important to decide now how the ponds will connect because there will not be much room for error later.
Dig out the holes for the two pond shells, checking often for levelness by dropping the shell into the hole and placing a carpenter's level across the top. Make sure both ponds will fit snugly into the holes side by side.
Use a jigsaw to cut a U-shaped section from each of the rigid pond shells where they will open into one another.
Cut a piece of flexible PVC pond liner to patch the two shells together; the liner should be at least 30 cm (12 inches) longer and wider than the area to be patched to allow room for sealing and overlap.
Clean the area to be patched using simple white vinegar and a cloth. The area must be clean and dry for the best seal.
Apply a layer of PVC contact cement (available at your local hardware shop) to the inside edges of the two pond shells, being sure to coat the entire surface evenly to prevent leaks.
Press the flexible PVC liner firmly over the glue, smoothing out any wrinkles and working from the centre toward the pond edges.
Allow the PVC cement to dry thoroughly according to package directions before filling the pond with water.
Once you decide on a location for the pond, plan on moving the rigid liners as little as possible to avoid tearing or straining the flexible pond liner.