If you want to build a natural looking koi or goldfish pond on your property, then there are many things you need to consider. The first considerations involve the size and location of the pond. If you want a low maintenance water feature that includes plenty of fish, then you should think about making the pond at least three feet deep. This will provide your fish with plenty of space to grow, and the pond will not warm up as quickly from the sunlight and allow algae to grow in an uncontrolled manner. A decent water volume of 1,000 gallons or more is ideal too, so make sure that width, length, and depth allow for this. Once the size is established and you have found a good place for the structure, then get to work on excavation and consider the following information about pond liners.

Choose the Right Liner

Koi pond creation starts with excavation and the removal of all the dirt, clay, sand, and rock from the earth. A large and dirty hole will be left behind once the excavation is over. This hole cannot simply be filled with water. The earth will naturally allow much of the water to drain out of the pond, since the natural water table likely sits many feet below the bottom edge of the hole.

To prevent this from occurring, you will need to place a liner across the bottom. Some people choose to place hard plastic liners. However, this requires you to pick a pond shape and size that is exactly the same as a liner that is available to you. Shipping and transportation of large liners may be an issue too for bigger koi ponds. If your pond has been dug with a large and freeform design, then you will need a flexible and waterproof liner that is cut and spread on the bottom. You have several different options available to you.

Flexible Liner Options


There are several different membrane options that you can pick from once you build a koi pond. Low density polyethylene liners are one of them. These products feature a waterproof polyethylene fabric that is formed from a tight weave. Usually, the weave or fabric is covered with a seal that keeps the polyethylene from becoming damaged by the UV rays of the sun. The liner is also somewhat flexible and small holes and tears in the material will not spread due to the tight weave. Polyethylene materials are quite common and relatively cheap to produce, so these liners are typically cost effective. 


PVC liners are an option too, and they are thicker than polyethylene varieties. This may be a good choice if you choose to add rocks, stones, and other natural elements to the bottom of the pond that can shift around against the liner. The PVC material is also able to stretch a small amount since one solid piece of material is used to create the liner. This can help to reduce ripping issues if something were to pull or press against the bottom of the pond. However, the liner is more expensive than a polyethylene one, and tears may spread if they do end up developing.


Rubber liners are available as well, but these liners are typically the most expensive due to the high demand for the materials in other manufacturing fields. Rubber pond liners are the thickest varieties you can purchase, and they are able to withstand a great deal of sun exposure and general wear and tear. This means they are likely to be the best value if you want a long term guarantee on the installation. In fact, many professionals use rubber liners themselves when creating ponds for their customers. 

Underlay Tips

You need to make sure to secure an underlayment across the bottom of the pond, regardless of the liner that you choose. This will help to decrease the amount of stress and pressure that is placed on the device from both above and below it. One of the most important aspects of the underlayment is to keep rocks from penetrating the liner membrane. Sand can often be used to soften ground that contains a great deal of rocks, and a fleece or fabric underlay should be placed over the sand. Afterwards, your liner can be secured in place and water can be added to the pond.