Generally, you can keep koi in any pond that is large enough for the number and size of the fish you plan to keep. This means that the construction method must allow you to build a pond that is big enough. Most preformed ponds are on the small side, so unless you are only going to keep just a couple of koi, this is not going to be a suitable type. Flexible liners may be used to build larger ponds, or you can use concrete to construct them.

If you are into DIY, and don’t want to employ a company to do the work for you, you should have a look at what koi pond kits are available. These normally offer all the pond construction equipment you need to build your own koi pond. The most usual types come with a flexible pond liner, and you will find them alongside most other fish pond supplies. But be sure to compare different kits accurately. Make sure you know what materials and equipment you will be getting, and how much you will pay for it. Pump sizes may vary and so may filter types.

Here’s an example of what you might get in a quality koi pond kit:

• an energy-efficient pond pump,
• a biological filter (to keep the water in your pond clear and clean),
• a skimmer unit usually with filter brushes,
• all the plumbing components (including pipes and connectors) you need to install the pump and filter,
• a skimmer box,
• a cover (possibly a fake rock) that covers the skimmer where water flows out of the pond towards the pump,
• a suitable flexible liner,
• a fabric or geotextile underlay (that gets laid underneath the liner),
• an underwater light (so you can see your gorgeous fish at night),
• start-up water-treatment chemicals, and
• well-prepared instructions that will show you exactly how to put everything together.

Sizes vary, but could range from 6 ft x 6 ft to 21 ft x 26 ft.

Sometimes dealers will supply fish with the kit, and then they may also include some koi food. But do not take this for granted.

Remember that koi are ornamental fish that grow quite large, so their eventual size must be considered when you plan the pond and eventually stock it. If the pond is too small, the fish simply will not thrive, even if they continue to grow bigger.

Unlike goldfish, koi need care, so do some reading about these incredible fish to be sure you are fully prepared.

If you have a swimming pool or a fish pond in the garden, outdoor lighting takes on a whole new meaning. By lighting up the water and the surrounding area, you can highlight plants and other features and enable people to see the fish at night. By installing a pool light in the water itself, you will add an even more magical element into the garden.

While landscape light fittings are normally only available from specialist landscape or light stores, outlets that specialize in fish pond supplies have various pond lights that may either be fitted within the pond, or allowed to float on the water.

First of all you need to decide whether you want pond lighting:

• in the pond,
• floating on the water that is in the pond, or
• outside the pond itself.

If you want lighting out of the pond, all the landscaping lighting possibilities are possible. For example you can install:

• a spotlight that focuses on a feature next to or in the pond,
• backlights behind plants around or in the pond,
• uplighters that are mounted low on the ground so that they shine upwards creating a dramatic effect,
• grazing lights that are aimed nearly parallel to the surface so that they accent the texture and surface color of the water in the pond,
• moonlights set in the upper branches of trees so that they shine down on the water imitating the light of the moon, or
• ordinary lamps that simply light up the immediate area in and around the pond.

Many landscape-type lighting systems operate on 12 volts, which makes it low voltage and therefore safe around water. But you will also need a transformer, and you may need an electrician to install the lights. A typical 300-watt transformer will power 12 lamps operating at 20 watts. It is usually best to buy a system that allows more than you need, in case you want to add more lights at a later stage.

Alternatively you can buy solar-powered lights that don’t use electricity at all. There are many different options in many different styles. The beauty of solar power is that you harness the energy of the sun during the day and then use it at night to light up your home and garden.

While underwater lights are very common in swimming pools, not that many people opt for them in fish ponds. But in recent years, as low energy lighting options have become more accessible and less expensive, more and more people are now looking at the option of using LED (light omitting diode) lights in their ponds. As technology continues to improve, there are an increasing number of options available.

Solar-powered floating lights have become popular in recent years. There are those that come with their own solar panels and others that operate from a separate unit. There are also a host of solar-powered lights that look like rocks, water lilies or other supposedly natural features.

Last of all, you can buy floating candles that look amazing in ponds at night. The only probably with these is that if the wind blows, they tend to go out.

Preformed ponds

Many people opt for preformed 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. 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 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 America, 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 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.

Concrete, bricks and mortar

Concrete is another popular material for 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.

But when you plan a pond for fish, you need to know what sort of fish you are going to keep. For example goldfish are a lot less demanding than koi, which are also a lot more expensive. Nevertheless, planning a pond for goldfish will take as much thought, care and imagination as planning a pond for the most collectable koi available. And in both instances you will need to source good quality fish pond supplies. You also need to know how many fish you are going to keep.

If you decide that you want a goldfish pond, you can opt for any construction type, and any size, shape or style you can imagine. You can use flexible liners, preformed ponds, or build elaborate designs using bricks or blocks, concrete or even natural stone. Even barrels and portable pots may be used to keep a couple of goldfish successfully – provided they can hold water.

Goldfish are not demanding, and if you forget to feed them they will scavenge and usually survive quite happily on food (insects, larvae and so on) from their immediate environment. Some people don’t even bother to feed goldfish any supplementary food.

Another factor is that you don’t need to incorporate an expensive pump and filter or do any elaborate landscaping unless you want to. Nevertheless imaginative planting around a goldfish pond will make it look more attractive and will encourage other water wildlife, like amphibians (frogs and toads), colorful and fascinating dragonflies and pretty damselflies, and other insects. All this helps to establish a good balance of nature.

If you are able to build different levels into your pond, do so. This will enable you to introduce a mix of floating, aquatic and marginal plants, some of which thrive in shallow water and others in deeper water. Fish also like to move between shallow and deep water, and this, combined with the plant life will usually result in fish spawning and multiplying very successfully.

Many goldfish ponds successfully incorporate other features including fountains as well as rockeries and waterfalls, decks and even bridges. They can also be used to grow colorful plants like water lilies, which flourish in sunny conditions. Like goldfish, water lilies will grow just about anywhere, provided they have water and enough soil for their roots to establish.

Of course, when you plan a pond for goldfish, you need to be sure that it fits the style of your garden or other outdoor spaces. Goldfish won’t care what it looks like, as long as it is watertight and there is lots to eat and places to hide.

Remember that goldfish will survive and flourish just about anywhere. So if you want the tiniest pond, that’s fine; if you want a pond that takes up your entire backyard, that’s also fine. The secret is to make it work for you and your family.

Before you decide what sort of pond you are going to build (or have built), it’s a good idea to compare all the different methods in terms of:

1. Cost,
2. Availability of materials,
3. Ease of construction,
4. Final effect, and
5. Any other pros and cons you can think of.

To do this, your first step will be to locate suitable fish pond supplies. You can then either work with what is available or look further afield to find exactly what you want – and need – for your chosen pond type.

In broad terms, the most common construction methods people use to build garden fish ponds involve:

• Installing flexible liners, EPDM (an ethylene propylene polymer) being the most common in the USA,
• Installing rigid liners or preformed ponds usually made from either fiberglass or some type of thermoplastic material,
• Constructing ponds from bricks, blocks or from either real or simulated stone units, and
• Building them from concrete that is cast on site.

Where flexible liners and preformed ponds are used, these are the only materials you need to create an impervious, watertight shell. But when ponds are built using the other specified materials, it is necessary to plaster the inside of the shell and/or seal them with some other suitable material. Rubberized bitumen is a common choice for plastered pools, although some people prefer the more expensive option of using a glass fiber coating.

From this you should immediately be able to see that the least expensive options are to use liners of some sort. While flexible liners are the least expensive (some being more pricey than others), preformed ponds are more likely to last longer than those constructed using a flexible liner. But preformed ponds are generally quite small and you are limited by the shapes supplied.

Having established the cost and availability of the materials you plan to use, you need to be sure that you can work with them, or find someone to do the job for you. None of the construction methods mentioned here is particularly difficult, although concrete-work and laying bricks, blocks and stone units all require some basic building skills – and a bit of experience. Concrete-work can also be quite heavy work.

Final effect is very important, and you need to know what you are aiming for. The most basic choice is between a formal pond and an informal pond, and you should be guided by the existing layout of your garden or backyard, and any obvious style of your house and other buildings.

Both flexible liners and concrete are good options for informal ponds because they can be formed to create any shape at all. While bricks, blocks and stone may also be used for informal structures, these materials are particularly appropriate when it comes to building more formal structures. Where flexible liners are used for formal structures, they are usually part of another building system. For example a liner may be used to seal a formal rectangular pond made from timber, or even the inside of a brick-built pond.

So decide what you want and what is feasible. Compare costs and then make up your mind what to build.

When you start looking for fish pond supplies, you will find that there are two basic types of pump that are suitable for garden ponds. The one type is submersible, which means it is located in the water, inside the pond. The other type is located near to the pond, but above the ground. Some suppliers also have combination pumps that operate equally well under water and on land.

Whichever type you choose, you will find that the pump output is described in gallons (or liters) per hour – depending where the pump was manufactured. So before you buy a pump, you’re going to need to work out what sort of volumes of water need to be moved or re-circulated. Remember that you will need the entire volume of water in the pond to be circulated in an hour.

Pumps will usually state on the packaging what the water head is. What this means is to what height the water in a fountain can spurt from the fountainhead nozzle, just above the surface of the water. If it isn’t powerful enough then you won’t get enough water spurting. If it is too powerful, the pressure will cause the water to spurt high into the air, rather like a burst pipe. This information is also important if you are going to create a waterfall, because you need to pump it to the top of the rocks so that it can tumble down naturally.

Submersible pumps are quiet and they normally have quite long waterproof cables that allow the pump to reach to the bottom of the pond. They are generally easy to install and very simple to operate. Unlike surface pumps that usually have to be primed, this is not necessary with submersible models.

Most submersible pumps have a strainer on the inlet side to stop fish and any floating debris from being sucked up into the motor and other moving parts. Some models are sold with interchangeable fountain jet fittings that produce different effects, but you can also buy these separately. They range from high-spurting geyser jets to domes and tulip jets, all described by the shape of water fountain they produce.

Surface or online pumps are a lot more powerful than most submersible pumps. On the down side, they are generally more expensive and a lot noisier as well. Only combination models may be used under water. But if you need to pump a lot of water any distance, then you will need a surface pump and you will have to find (or build) some sort of housing for it to protect it from the weather. Ideally surface pumps should be located just below the surface level of the water, near to the pond, but in a position where there is no risk that the unit will get wet.

Whatever type of unit you decide on, you will need to run power cords from an electric power point. The power point may be located inside the house or you can mount a special waterproof box on an outside wall to avoid having to run cord (or cables) through the wall. Where wiring is buried underground, conduits must be used to protect the wiring and to prevent it from coming into contact with moisture in the ground.

Don’t ever forget that the combination of electricity and water is potentially lethal. If you aren’t 100% sure what is involved installing a pump, call in an electrician.

Mechanical and biological filters work completely differently to one another and the media they use is specific to the filter type. So when you get your fish pond supplies, you must be sure to buy the right media for the filter you are using.

The main difference between a mechanical and a biological pond filter is that:

• a mechanical filter will sieve out or strain the dirt and algae, and
• a biological filter will break down this same dirt and algae and basically neutralize it.

The simplest mechanical filter has a type of open-cell foam (which is the filter media) set over the pump strainer. When the pump is operating, all the waste is literally pulled into the foam. A more complicated and more effective mechanical filter is made by layering different types of filter media in a casing of some type. Usually there will be open-cell foam at the base of the casing, with fine gravel or some other type of filter granule on top. Mechanical filtration will occur in the top gravel layer and, if the pump runs continuously, a certain degree of biological filtration will take place throughout all the filtration media as well.

The way biological filtration works is that the waste products are turned into harmless materials by the action of the bacteria that flourishes on the filter media. But to be effective, the filter (and therefore the pump) needs to run continuously. If the pump is switched off, the bacteria will die in just a few hours, and it will take several weeks for it to become effective again.

Biological filters can work with either submersible or surface pumps, and either way, the water is pushed or drawn through the inlet pipe into the filter at the top, and then aerated through jets or holes that pass through one or more layers of suitable media. Several types of media may be used, depending on the design of the filter: for example rough gravel, open-cell foam, resin-bonded fiber matting, coarse sand, and other specially manufactured granules. The water passes through whatever media is in the filter, and the clean, purified water returns to the pond through the outlet pipe at the base of the filter unit.

More advanced biological filters consist of several chambers with valves, but they still use the usual filtration media.

The size of filter you choose will depend on the volume of water in your pond and the number of fish you keep in it. If it doesn’t have the required capacity it simply won’t keep the pond water clean. Also remember that every type of filter needs to be cleaned regularly, and the filter media needs to be replaced whenever it is necessary. Usually you will be able to tell that the filter media is dirty because it no longer does its job properly and the water starts to become murky or green.

So if you are going to plan a koi fish pond, you need to be as thorough as possible as it will involve an investment in both time and money – in the building phase as well as later on. If you aren’t prepared to go the extra mile, rather build a goldfish pond. These may not be as rewarding, but they are certainly cheaper and require a lot less effort in terms of setting up and stocking with fish and fish pond supplies, as well as being easier to maintain over time.

But first consider the joys of koi.

Over the years, the koi breed of fish has been carefully developed by selective breeding and there are many different forms and colors available today. Those in the know can quickly identify good color and markings, which immediately increase their price tag for both buying and selling. If you’ve never studied the color and markings of koi before, you will be amazed to see the variety: from metallic gold and silver to red and orange, black and white – with some really unusual mixtures in between.

Generally koi ponds are larger than ponds planned for goldfish. This is primarily because koi grow a lot bigger. They can grow to as long as 36 inches (90 cm) and it is generally accepted that they need a depth of at least 5 feet (or 1.5 m), although where freezing is not an issue, you can get away with about 3 feet. It is very important to design a koi pond to a size that will accommodate not only a certain number of fish, but also their eventual size. Don’t ever allow crowding of koi because they simply won’t thrive the way they should. An accepted rule of thumb is that you need to allow at least 27 feet (or 2.5 m²) for every fish.

In addition to size requirements, koi ponds should never be one standard depth. For this reason it is best to try to plan different levels, or at least a shallow shelf around the outer edges of the pond.

Another aspect to consider is that predators, in the form of large birds and small mammals, will inevitably prey on the fish. Since these fish are relatively expensive, koi enthusiasts generally opt for netting over the pond to protect them. Any sort of netting or mesh should be positioned so that it is about 7-10 inches from the surface of the water. Unfortunately this does detract from the appearance of the pond, but it can’t be helped.

When it comes to choosing a construction method for koi ponds, just about anything goes. However, since you will probably want a reasonably substantial –sized pond, preformed ponds are not suitable. For more information on fish pond construction and fish pond supplies, please click here to see more articles.

Before you decide what kind of pond to buy, do some homework to see what is available and at what kind of cost. If there are limited supplies in your area, then the obvious solution is to turn to the Internet to see what you can find there. Be sure to weigh up all your options before you make a final decision.

If you are indeed wanting the pond for fish, you will need to be sure it is large enough, and deep enough for the fish you intend to keep. Generally preformed liners are relatively small and better suited to goldfish than to koi.

In America, the most common type of preformed pond is made from fiberglass and some distributors sell them with a pump and filter. While koi lovers generally filter the water in their ponds, so they can see the beautiful colors of the fish and keep them healthy, this is really not necessary when keeping ordinary goldfish.

Fiberglass pond shells are often built up layer-by-layer by hand using glass-fiber reinforced polyester. Alternatively they are formed by spraying several layers of a special catalyst, a polyester resin, and chopped strands of glass-fiber onto a mold. The result is a tough, rigid liner ideal for the smaller garden.

Various thermoplastic materials are also used to make preformed fish ponds, including polypropylene and high density polythene. These are normally vacuum-molded, which is a cheaper process than molding fiberglass, and the resultant material is not quite as rigid or resilient.

Both types of molded liner come in a variety of shapes and sizes, some with different levels that can be used for plants. Black is a popular color because it looks natural in the ground. However, a rim sticking out above the level of the ground is always a dead giveaway, so take this into account when you make your choice. You will need to hide the rim either with clever planting, or by laying some kind of edging or paving. This will depend how informal and natural you want the pond to appear.

Some specialist manufacturers mold architectural pond features, including fake rocks from glass-fiber reinforced cement, and they also mold small natural-looking preformed ponds from the same material. These are generally even smaller in size than fiberglass and molded plastic ponds. But they can make an attractive water feature in the yard.

Once you know what is available from your local fish pond supplier, you can make a decision in terms of what to buy. Installation of all types is exactly the same. Briefly, all you do is to turn the pond upside down and mark the perimeter on the ground. Then you dig out the earth to the depth of the pond, leaving a shelf if the levels inside vary. It is best to dig out more soil than required, so that you can add a layer of soft building sand to cushion the pond. Then position the pond and backfill with soil or building sand, ensuring the mold stays level.

A good quality rigid liner (made of fiberglass for instance) may also be installed above the ground – or partly above the ground. This can be quite effective if you want a relatively formal brick-finished pond, or one that is clad with stone; you can use the real thing or one of the many simulated stone products that is available.

Then all that’s left to do is fill the pond with water and add water plants if you wish. Allow plants to establish themselves before introducing fish.

In broad terms, building a pond will involve either:

• laying some kind of flexible liner or creating an impervious layer,
• installing some type of preformed shell, or
• building the pond using either concrete or bricks and mortar.

Whichever option to decide on, you need to be sure that the pond will hold water without leaking. That might sound obvious, but many a pond project has failed due to leaks, some of which occur quite a while after completion of building work. For example animals (especially dogs) often jump into ponds and damage flexible liners. Some inferior-quality preformed ponds eventually become brittle and crack. And ponds built with concrete, bricks or blocks and mortar, deteriorate and start to leak. So you need to be aware of these potential pitfalls before you decide exactly what to build and how to build it.

In addition to the materials we can use to either build or install fish ponds, there are other waterproofing solutions that we can use to make sure our structures remain watertight over time. Here are some examples. In all instances you must be absolutely sure that materials are non-toxic, otherwise fish won’t survive.

Waterproofing additives

There are various materials that you can add to concrete, mortar and plaster mixes to make the finished surface less porous, plasticizers for example. The only problem is that they are not usually 100% successful on their own, so it is best to overcoat with some other material as well, like bitumen, a specialist waterproof paint, or with fiberglass.

Rubberized bitumen

One of the most effective materials for sealing concrete and other plastered ponds, rubberized bitumen is simply painted onto the finished surface. It may also be used to seal ponds that are lined with geotextile materials. Just be sure to use a water-based product.

Generally the first coat is diluted with water, and the more coats you apply to the surface, the more waterproof the finish will be, and the longer it will last. But you will need to follow the manufacturer’s instructions as these may differ.

Paint

In the early days of swimming pools, concrete structures that were plastered and painted with specialist rubber-, epoxy-, vinyl-based or even acrylic paints were quite common. Some paint companies still manufacture these paints and they can be used with some success to seal plastered ponds. Be careful with colors, especially if you are aiming for a natural look. Dark hues give the most  natural effects.

Moisture-curing polyurethane

This is another option for waterproofing plastered ponds. There are various products, and because they were developed for use in dams and to seal tanks used to store drinking water, they are non-toxic and generally resistant to chemicals.

The most common products require you to coat the plastered surface with a special primer before applying the polyurethane. Again, be sure to follow the manufacturer’s instructions.

Fiberglass

Used to make preformed ponds, fiberglass may also be applied on site over smooth concrete and plaster to make sure surfaces really are watertight. It is ideal for sealing around boulders and both real and fake rocks that are used around the perimeter and inside of ponds.

There are various methods of application, all of which involve a catalyst, resin and some sort of fiberglass matting. As always, follow the manufacturer’s instructions.

Putty and silicone sealers

Two-part epoxy putty may be used to plug small leaks or fill small holes or cracks.

Silicone sealers are ideal for sealing around pipe-work, for example when you install a fountain in a pond. Just be sure to use a sealer that is manufactured for exterior use.