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Fish pond liners - Types and dis/advantages

When planning on your project for building your own fish pond one of the choices you have to incorporate into your plans is which type of fish pond liner that you are going to use. Concrete built ponds tend to be a better option for the large Koi fish ponds but for the more basic and smaller fish ponds, flexible pond liners or preformed pond liners tend to be the more popular choices.

Building a concrete Koi fish pond will be covered in a future article but for now this article will concentrate on the flexible and preformed fish pond liners to give you as much information as possible when it comes to making your final choice.

The size of the fish pond that you are planning to build can sway the decision one way or the other as does the actual budget that you are working to; all of these factors need to be taken into consideration. Smaller ponds that are shallow tend to do better with preformed fish pond liners, the only drawback with this is that you are restricted to the shapes of liner that are available, flexible liners give you more scope for individual shapes and flexibility, they are often a cheaper option to choose as well. The main reason that people decide to add a fish pond to their garden has to be for aesthetic reasons, the fish pond adds a feature to your garden as well as providing you with a hobby that is very rewarding.

Pond liners do need looking after and will have a limited guarantee, admittedly this can be for a number of years but this also needs to be taken into account, regular pond maintenance will ensure that you get the maximum life out of your pond liner so should always be performed on a regular basis.

When pricing up for your fish pond liner remember to account for any underlay that may be required, if at all as sand and old carpeting can also be used in some cases, there is no point paying out for the fish pond liner if you cannot protect it from underneath once it is in position and full of water, sharp stones etc. can easily damage and puncture your fish pond liner.

Preformed fish pond liners

Preformed fish pond liners are made from a very durable plastic that should be weather proof and have some resistance to the UV rays emitted by the sun. They are available in a large variety of shapes and sizes, most manufacturers nowadays try as much as possible to give their products a natural look with shelving that fits into the feel of the fish pond and usually offer a couple of different depths with the liner that allows the fish to inhabit deeper waters in the cooler months and swim in the shallower levels during the summer months. A decent quality preformed fish pond liner should be made from a sturdy thickness of plastic, they will bend slightly but once full of water should be rigid enough not to move once settled into place.

Fitting a preformed fish pond liner into position is quite a straightforward affair as long as accurate measurements are taken during the excavation, there will be varying differences in the depths along the pond liner and each one will need to be measured as well as the width and length. Allow an extra couple of inches to each measurement as the excavation will also need a layer of sand adding on the top to prevent any sharp stones or debris from protruding and damaging the liner. If a large preformed liner is being used then it is better to ask for help with the positioning, this makes the job twice as easy if there is someone holding the liner at either end, once in place the liner can then be filled with water. It is best to leave the preformed liner protruding above the surface for a couple of inches as once filled, the liner may sink slightly with the extra weight., fill the liner slowly and keep backfilling with sand underneath so that all of the area is supported including any ledges.

Using a preformed liner can make the task of building your fish pond easier but like any product they do have their advantages and disadvantages.

Advantages of using a preformed fish pond liner:

  • Preformed fish pond liners are very rigid and tend to be thicker than a flexible fish pond liner, if a small sharp edge underneath the liner has been missed they may not puncture, with a flexible liner it is more likely to leak from such an edge.
  • Installing a preformed liner is quicker than using a flexible fish pond liner and the final result can look more natural especially with the new designs of liners that are now available.
  • Designing your fish pond is done for you, shopping around and looking at all of the designs available will give you an instant insight into what your completed fish pond will look like.
  • As preformed fish pond liners tend to be shallower and smaller than fish ponds that use flexible fish pond liners, keeping the fish pond clean and performing maintenance on water pumps etc. tends to be easier.

Disadvantages of using a preformed fish pond liner:

  • The most obvious disadvantage of using a preformed fish pond liner has to be the higher prices compared to the pricing of the flexible fish pond liners. The preformed liners are more expensive but you are paying for the work being done for you, if you are on a tight budget this can work against you.
  • You are limited to the designs that are available, if you are after a unique design for your fish pond then this will not be the option for you, if you are happy with the designs that you have found then this disadvantage has been ruled out.
  • It is critical with a preformed fish pond liner to get your measurements correct, it needs to sit with full support in all areas and be perfectly level once filled or water will appear to lean to one side or even drip over the edges. The edging itself is always narrower than allowed for with a flexible liner so this can also create problems if you are trying to disguise the edging from view, with a bit of ingenuity this problem can also be overcome.

Flexible fish pond liners

Flexible fish pond liners tend to be used in the larger and deeper fish ponds, also in fish ponds that are original or have an unusual shape. They allow for a wide creativity range from the designer and, dependant on the material used to create the pond liner, usually fall into the cheaper pricing bracket and they can be ordered for the actual size required for your fish pond project without too much excess to discard afterwards.

Originally the flexible fish pond liners were made of thinner butyl or even PVC and could not carry a long guarantee of being water proof, some were rated at 10 years while even cheaper materials would only be guaranteed for as little as 5 years, not very effective once the fish pond is all set up and running. Nowadays the fish pond liners are made to a thicker dimension giving them much longer guarantees, admittedly this does involve paying a higher price initially but at the end of the day it is far better to pay more for a fish pond liner that can last up to 30 years at least than pay for a cheaper version that needs replacing at shorter intervals.

For smaller ponds the thinner liners are more suitable and the choice of thickness is still offered, thinner liners are more flexible for the really small corners etc. that are found in small fish ponds.

Using the flexible liners is easy as long as you know which size you require for the fish pond that you are planning. There is a basic equation that has been worked out to help with the size required and makes ordering very easy.

To work out the size required measure the longest length of the fish pond and do the same with the widest part of the fish pond, you can now use this simple equation to work out the size.

Length of liner required - Length + (2 x depth) + 2 feet (1 foot either side for overhang)-Answer A
Width of liner required - Width + (2 x depth) + 2 feet (1 foot either side for overhang) - Answer B

To work out the square feet required simply multiply answer A by answer B

As mentioned above the flexible fish pond liners can be manufactured from various materials and these will be priced accordingly, when selecting your pond liner bear these points in your head.

Butyl liners are very tough and weather proof, they are capable of withstanding frosts and the UV rays of the sun. The only downside with their strength is that they can be difficult to fold into corners or awkward areas when you are filling the fish pond, but they still can be maneuvered to give you neat folded corners with patience.

PVC flexible fish pond liners tend to be the most popular choice, they are very flexible and folding them neatly is an easier task than with the butyl liners. They are also weatherproof but the guarantee tends to be shorter than with the butyl liners and you may need to replace them every 4-5 years.

All flexible fish pond liners require a good underlay beneath them to protect the liner, this can be several inches of soft sand, even old carpeting or similar can be used, as long as the underlay is thick enough to protect the pond liner from any sharp objects it will be fine. You can even purchase an underlay specially designed for fish pond liners so if you decide to use this, allow for the extra cost in the budget.

Laying a flexible fish pond liner needs to be done slowly and patiently. It should be stretched over the excavation and slowly filled with water, as the liner fills keep tucking it down and any corners folded neatly, the slower that you fill the fish pond liner, the easier the task is. Once the task is complete you should finish up with an overhang all the way around the fish pond. This needs to be weighted down to prevent it from slipping back into the fish pond. Rocks or paving slabs are ideal, you can bury the overhang with soils but this tends to move in time.

As with the preformed fish pond liners, the flexible fish pond liners also have their own advantages and disadvantages. They are as follows:

Advantages of using a flexible fish pond liner:-

  • The flexible fish pond liner can be ordered to the size that you require, excess liner is kept to a minimum to reduce the costs.
  • Any shape of fish pond can be catered for with a flexible fish pond liner,. They are better suited for the deeper fish ponds and can be tucked into any corner or curve of your design.
  • You are not restricted to a pre-made design of fish pond; you can design away to suit your needs or to make the best use of the space available in your garden.
  • The flexible fish pond liner always comes with a guarantee; many of the thicker flexible fish pond liners are now available with life time guarantees.

Disadvantages of using a flexible fish pond liner:-

  • Flexible fish pond liners tend to look less natural when in place, there are new types now available that attempt the natural look but this can sometimes be lacking.
  • They can be difficult to straighten out in the fish pond, with a few helpers the job is a lot easier but it still can be time consuming.
  • They tend to take longer to position compared to the preformed fish pond liners.

Hopefully this article will have answered some of your question about fish pond liners, if you do need to ask anything please add your comments to the provided box below!