KEEPER BASICS: BUILDING A POND

In this month’s “Keeper Basics” we look at something a little different. Anyone who has been out herping in the UK or the tropics will understand that fresh water is often a treasure trove for reptiles and amphibians. Not only do most amphibians rely on streams and ponds, but many reptiles predate on these amphibians. Here in the UK, a good pond can encourage frogs, newts and grass snakes. Fresh water can also bring an abundance of invertebrates that support lizard populations, as well as native birds and mammals. Generally, these ponds will be at their liveliest without introduced fish, but even a goldfish pond can provide some much-needed freshwater to garden visitors. Ponds can also be fenced off, with a biosecure perimeter and make excellent turtle enclosures or provide a home for a whole host of different exotic animals. However, building a pond is rarely as simple as digging a hole in the ground. So, here is a stepby-step guide to producing a nature pond in your back garden.

It’s not all about size

Anyone with some outdoor space should be able to build a pond that benefits the environment. Some ponds may be better suited for some species than others, but all bodies of water hold intrinsic value. Whilst a large lake with plenty of fish and reedbeds will attract grass snakes (Natrix natrix) and waterfowl, amphibians only require very small ponds or bogs to thrive. In fact, threatened great-crested newts (Triturus cristatus) will often occupy the most unlikely waterways, including ditches on the side of the road. Even a ceramic planter on the balcony of an inner-city flat can hold massive value to birds and insects in urban environments. It’s not about the size of the pond, but what the person does with it.

Choosing a location

Choosing a successful location for the pond is important, as it is no easy task to dig out and reinstall a pond once it has been built. Consider that sunlight will prompt algae growth, which is ideal for developing tadpoles, small fish and invertebrates but can sometimes be a bit of an eyesore and require more maintenance than a pond placed in a shaded area. If the main intention of building the pond is to attract reptiles and amphibians, consider a location that receives a good amount of sunlight either early in the morning or later in the evening. If the pond receives over six hours of sunlight and is a reasonable size, waterlilies may bloom. Not only are these aesthetically pleasing for the person building the pond, but they offer valuable shelter for herptiles and inverts. Whilst a nature pond should generally be placed in a quiet location, planning a discrete sitting area to observe the wildlife is another helpful consideration.

If the primary goal of the pond is to house fish, the keeper should consider a much more shaded area. This will maintain cooler water, inhibit plant growth and can be built closer to the home. Here, the builder must consider electrical equipment such as pumps and filters which may need to connect to the house. This will also require a qualified electrician to install the wiring and avoid hitting any underground services (sewers, pipes, cables, etc) as they do. If the keeper is hoping to add fish to their pond, it is important that necessary research is done first. Some species will need better filtration and air flow, others will need greater depth, etc. The builder should also consider the safety of any young children who may visit. If young children or relatives are present, consider choosing a raised location, or one in near-constant view of the house.

Taking shape

Next, the builder must choose a shape for their pond. Those building fishponds should consider a raised design. In many cases, you may want to prevent amphibians from accessing the pond as their spawn will quickly be eaten by pond fish. A raised pond is also likely to be safer and easier to install electrics. As the builder will be limited to a handful of plants and will no doubt aim for clean water with an unobstructed view of the fish, the shape of a traditional ‘fishpond’ is mostly about aesthetics. Consider what it looks like from inside the home (both upstairs and downstairs), whether it can be accessed from all angles and where the ‘water line’ will sit. Although the pond should have a shelf of shallow water to allow plant growth, a more uniform rectangular or circular design will work well and can allow for water feature installations too.

A nature pond can be much more creative but still requires some thoughtful planning. For example, the pond should be constructed in layers. Having several different shelves of water depths to provide plenty of ecological niches for the inhabitants to occupy. This also provides the best opportunities for plant growth. There should be at least one sloping edge to provide wildlife with access to the water (and allow small mammals to escape). In ceramic planters or preconstructed pond designs, this can be provided with décor such as driftwood.

A boggy area will also provide more opportunities to add a variety of plants. A slope from the top shelf, out towards the perimeter of the pond, should help create this bog. Adding plenty of rocks, logs, rotting wood, etc to this area will also ensure that there is an abundance of prey items and refugia for newts and froglets. Finished nature ponds often look much smaller than the builder anticipated. Those with boggy perimeters or dense vegetation will look even smaller and so it is important to utilise as much space as possible.

Balcony-friendly container ponds do not require the owner to plan a shape – simply fill a container with fresh rainwater, install a few plants and they are ready to go. However, the owner could consider placing several containers next to one another. For example, three ceramic planters placed together on a balcony could contain different plants, different depths and perhaps a decorative element to link all three. This will maximise the biodiversity of this micro-ecosystem.

Building time

Depending on how elaborate the pond design is, the building process will vary slightly. However, the basic crux is: dig a shelved hole, add a liner to fill the perimeters of the hole, stretch it to the very corners of each shelf and pin down with rocks, fill it with water and add plants. However, the easiest possible way of doing this is to buy a sturdy, pre-constructed pond from a garden centre. After installation, décor can help fill some of the ecological niches that can be achieved with the liner method. For the most natural-looking nature ponds, try this method:

1. Outline the perimeter of the pond with rope or sand

2. Dig the entire diameter of the pond to the depth of the first shelf. This will depend on how large the pond is, but around 10 - 20cm is a good depth for this shallow shelf (whichever depth is used, it MUST be consistent across the entire perimeter of the pond to ensure the water sits neatly at one level. The first shelf will hold the hardscape and will outline the surface area of the water, so ensure that this shelf is wide enough to be filled with rocks, logs and plants.

3. Create one sloping edge into the first level to allow hedgehogs or other animals to escape if they fall into the pond.

4. Working inwards, using the same rope/sand planning tools to mark out different shapes, begin digging more shelves until the desired depth of the pond is reached. All shelves must be straight and upright, like a set of stairs, to support plants. Be careful not to knock the shelf edges in whilst working on the deeper levels.

5. Remove any sharp stones from the hole.

6. Lay the geotextile pond liner, which is used to protect the actual liner from debris, roots and damage.

7. Choose either polyethene (cheaper option but cannot stretch easily) or butyl (more expensive, but easier to manipulate) liner and place it in the deepest part of the pond.

8. Standing upon the liner, begin to line the entire pond, pushing the liner into all edges of the pond.

9. Add some smooth rocks to the base and a few more to each shelf to keep the liner in place.

10. Fill with water, adjusting the liner after any movement, to ensure it remains secure and covers the entire pond. Anti-chlorinator can also be used, to ensure good water quality right from the start.

Edging a pond

Once the pond has been planned, dug, and lined, it’s time to complete the finishing touches. Place offcuts of liner beneath the hardscape to protect it from any punctures and begin building from the first shelf, out towards the top of the pond. There are lots of ways to do this, so using a variety of hardscape shapes and sizes will help give the pond a natural feel. After a few days, once the owner is certain that the pond is not leaking, the edges of the lining can be trimmed down, and the basis of the pond should be complete. Ensure there are no areas of exposed pond liner – the sun’s UV can break these down over time and create a leak that may ruin the pond. Instead, place extra rocks and hardscape around the perimeter.

Other considerations

The deeper the pond, the easier it will be to maintain. However, a deeper pond is likely to be more expensive and time-consuming to build.

• Shape nuances are often lost. For an aesthetically pleasing fish pond, try using materials to build a simple shape. For a nature pond, expect that the final result is unlikely to look like the envisaged idea.

• Consider adding an area close to the pond, which will collect ‘spill over’ water. This is most important for anyone building a nature pond close to their home.

• Ponds require some level of cleaning. Although nature ponds will require much less cleaning, creating a smooth bottom, with large, similarly-sized rocks will make this process easier.

• Consider filling in cracks with landscaping foam. This is a nice, easy way to prevent water from escaping and can be terra-scaped in a similar fashion to most terrariums.