Building Fish Ponds

All About Building Fish Ponds

Building fish ponds can be very satisfying and rewarding. There are many different types of fish ponds and a wide variety of construction methods that you can use to build or install them. Your choice will depend partly on whether you are going to call in somebody to do the work for you or do it yourself. If you opt to go the DIY route, you will need to take your personal skills into account. Your choice will also be affected by the available fish pond supplies in your area.

Preformed Ponds

Many people opt for preformed ponds when building fish ponds because they are so simple to install. All you do is dig the shape of the rigid liner to the required depth, make sure the base is level and compact, and pop the pond into the hole. Then you backfill around it, fill it with water, and you’re just about there. Preformed ponds are manufactured from various materials including fiberglass, glass-fiber reinforced cement and a range of thermoplastics.

Disadvantages include limited shapes and sizes and the fact that they can look fake if attention is not paid to the edges of the pond. But with imaginative planting or the addition of some type of paving around the perimeter, they can also look wonderfully charming.

Flexible Liners

Flexible liners are also easy to lay, and as long as the material can be successfully joined, you can create ponds of virtually any size. Building fish ponds with this method is very effective. The cheapest liner is polyethylene, or some other type of plain black plastic sheeting. There are various colors and gauges (or thicknesses), but generally it’s best to stick to reasonably thick black sheeting.

Not only does it look more natural in the ground, but black plastic contains carbon which inhibits the effect of harmful ultraviolet light from the sun. Some companies manufacture relatively thick plastic sheeting especially for fish ponds. Alternatively you can use vinyl sheeting (the type manufactured for swimming pools), which is more UV stable, but more expensive that polyethylene.

Butyl rubber is another flexible liner option. Available in various thicknesses, it is highly resistant to puncturing and won’t degenerate when exposed to sunlight. Often described as the Rolls Royce of pond liners, butyl rubber is understandably expensive when compared to other flexible liners.

In the U.S., an ethylene propylene polymer (EPDM) has largely taken the place of butyl rubber. Cheaper than butyl, but highly resistant to the sun’s UV rays, 45-mil EPDM is the standard.

Like ponds created using rigid liners, those made with flexible liners need to be finished off imaginatively.

Geo-fabrics and Bitumen

Another lining that you can use for building fish ponds is created by combining a geo-fabric material with several layers of a good quality rubberized bitumen coating. These materials are more commonly used by engineers to stabilize embankments or line large earth canals. Joins are not an issue because they will be sealed by the bitumen which is painted or broomed on once the fabric has been positioned in the required excavation.

While ponds of any shape or size may be created this way, it is important that the sides don’t slope too steeply. It is also vital that the bitumen you use is non-toxic otherwise you will poison the fish.

Sodium Clay

Lining ponds with bentonite or sodium clay is another possibility, provided the material is available in your area. Usually sold in powder form, the “clay” is mixed with soil from the excavated pond, spread over the surface and then moistened. Done correctly, it will create a natural skin that will prevent the water from draining out. See our story here: “12 steps to make a bentonite clay pond”

Concrete, Bricks and Mortar

Concrete is another popular material for building fish ponds. It is also used for the foundations of brick and block ponds. Concrete ponds should be excavated and shaped before the concrete is mixed and placed. It is also good practice to lay some sort of wire mesh over the excavation to keep the fresh concrete in place while it sets and hardens.

To make the surface impermeable, the most usual approach is to plaster the surface and then paint it with bitumen. Similarly, brick and block ponds should be plastered and then sealed with a bitumen compound. Here is our story of Penny building our one formal pond: “formal face brick pond only 11-steps”
Main Picture by: Wonderlane, Flickr