Posted by LoveMyPond, 30 Jun 2025

The Ultimate Backyard Koi Pond: Choosing the Right Liner for Fish Health

Are you a homeowner looking to enhance the look of your backyard with a healthy koi pond? If so, you’re probably wondering which pond liner to choose.

Pond liner has a lot more impact than you first might think. Choosing the right one is very important if you want to have healthy fish. The best choice? Rollgum EPDM liner. This liner offers excellent durability, stretch, and other properties that set it apart from the rest.

Why Pond Liner Matters

Why is pond liner so important? Choosing the right pond liner for your space can make a big difference in the overall health and quality of your pond.

Poor-quality liner can cause:

Cracks and tears that cause leaks
Chemical leaching that harms aquatic life
UV degradation from sun exposure
Premature breakdown, costing you time and money

Koi fish are especially sensitive to water quality and environmental changes, so their health can be compromised by a low-quality liner. That’s why it’s crucial to start with a liner that’s safe, reliable, and built to last.

Comparing the Different Types of Pond Liners

You might be surprised to find out that there are lots of types of pond liner. Before we dive into the best option, here’s a quick look at the common pond liner materials:

1. PVC (Polyvinyl Chloride)

Pros:

Low upfront cost
Flexible and lightweight
Easy to find at hardware stores

Cons:

Not UV stable – breaks down quickly in sunlight
Short lifespan – often becomes brittle in just 2–5 years
Contains plasticisers – chemicals that may leach into the water over time
Not safe for koi – long-term use risks harming fish and aquatic life
Difficult to repair and seam reliably

2. HDPE (High-Density Polyethylene)

Best known for its toughness, HDPE is a rigid, industrial-grade plastic liner.

Pros:

Very puncture and tear-resistant
Chemically inert – won’t leach toxins
Used in large-scale dam and industrial applications

Cons:

Extremely stiff – hard to shape into complex curves or contours
Difficult to install for DIYers – seaming requires welding and professional tools
Prone to stress cracking if not installed properly
Not ideal for smaller backyard ponds due to lack of flexibility

3. EPDM (Ethylene Propylene Diene Monomer)

EPDM is a synthetic rubber that ticks all the boxes for backyard pond projects, and especially for koi.

Pros:

Incredibly flexible – conforms to any shape, shelf, or curve
Fish and plant-safe – no plasticisers or harmful additives
UV and ozone resistant – stands up to harsh sunlight and weather
Lasts for decades – 50+ years with minimal upkeep
Easy to seam and repair – DIY-friendly
Maintains elasticity in extreme cold or heat

Cons:

Slightly more expensive upfront than PVC
Slightly heavier to work with than plastic liners

Why is EPDM the Best for Koi Ponds?

EPDM liners are a top choice for any koi pond design thanks to their non-toxic composition, flexibility, and exceptional durability. They work equally well in everything from formal rectangular pools to natural, free-form water gardens.

Here are some more reasons:

It’s non-toxic and inert, stopping it from harming aquatic life and plants.
It’s highly flexible, meaning it conforms to shelves, ledges, curves, and contours without stress points.
It stands up to Australia’s harsh UV conditions and fluctuating temperatures.
It resists punctures and tears, and even if damage occurs, repairs are quick and easy.

Rollgum EPDM: Premium Performance, Zero Compromises

If you’ve been browsing your options, you’ll probably know that there are many options of pond liners you can opt for. As we stated in the section above, they do have their benefits. However, there are many key reasons why Rollgum EPDM stands out as the top choice.

Let’s take a look at what sets this kind of liner apart:

Certified Fish Safe

Rollgum is made without plasticisers or harmful chemicals, making it completely non-toxic and safe for koi and other aquatic life. If you have koi, you need to be aware of their requirements. These kinds of fish are sensitive to their surroundings, so making sure that the liner you choose is appropriate is highly beneficial.

Unmatched Flexibility (400% Stretch)

Rollgum can stretch up to 400%, making it really easy to install. This means that if you have a pond that’s an unusual or obscure shape, Rollgum will keep its quality intact as it conforms to the natural contours. Unlike rigid liners, it won’t fold awkwardly or create weak spots.

UV and Ozone Resistant

Rollgum is so UV and ozone resistant that the first one was installed over 50 years ago in Spain and it’s still going strong today. With high-grade UV protection, Rollgum’s EPDM liner holds its look and strength, even after decades of exposure to the harsh Australian sun.

The liner is designed to maintain its look and quality in extreme temperatures ranging from below -40ºC to +150 ºC, unlike plastic liners that become brittle in the cold and stretch in the heat.

Tear & Puncture Resistant

Rollgum is extremely dense, and this helps to provide superior protection against rocks, roots, and wildlife, reducing the risk of leaks and tears. However, in the very rare situation when a tear occurs, it’s very easy to fix.

Simple to Install and Seam

Rollgum EPDM is compatible with professional-grade seaming products and adhesives, which makes it very easy if you want to put your DIY skills to use. This makes it easier to join sections securely for large installations and there’s no need for expensive jobs or tools like hot glues.

Multiple Thicknesses to Choose From

Choose the right thickness for your project:

0.8mm – Ideal for small to medium ponds (10-year guarantee)
1mm or 1.14mm – Perfect for large or commercial ponds (20-year guarantee)

Final Thoughts: Don’t Cut Corners on Your Pond Liner

With the right liner, you can create a healthy koi pond that thrives. EPDM is an excellent choice as it brings you decades of joy, especially as an aesthetic feature in your backyard.

The pond liner you choose is the foundation, so it needs to be good. Cutting costs on the liner you opt for can land you in a situation that damages the health of the koi fish, causes leaks, and leaves you with no choice but to rebuild the pond from scratch.