Designing a pond

How to get the design and planning stage right first time.

Building ponds

Where, how and what materials and equipment. The hard work bit.

Koi Pond Pumps

How to choose and where to buy your koi pond pump.

Koi Pond Filters

Selecting the correct filter for your koi pond.

Koi Pond Food

Choosing the right food to keep your koi fit and healthy.


Choosing Koi Pond Equipment

Possibly the most important decision is the equipment required for running the size of pond and filter system you wish to install. Once you have decided on the size and capacity of the pond, you can then choose the equipment to maintain the water quality. This section talks in brief about some of these items. For more detailed information, follow the red links.Koi Pond Picture

The main items you will require are a pond pump, pond filter, (or choose a combined pump and filter kit) an ultra violet or UV steriliser or clarifier and the necessary pipe work to plumb it all together. You will also need specialist waterproof electrical fittings to connect everything up.

If you are building a liner pond, then a good quality, preferably butyl rubber pond liner will be needed. Follow our liner size guide to help you work out what size of liner to buy. To work out the capacity of your pond, which will dictate the size of the pump, filter and UV you require, see our measurements and conversions page.


You will have to decide on how you are going to filter it. And yet again there are choices i.e. whether it is pump fed or gravity feed. A pump fed koi pond will require more maintenance compared with a gravity fed pond, yet the construction costs of a gravity fed pond need not cost a lot more.

FilterThe other advantage of a gravity fed system is that it is installed below ground surface level and so is less unsightly. A pump fed system is usually installed above ground level and so more cost is involved in covering everything up to keep it out of sight.

The main difference is the cost and effort of fitting a bottom drain and the necessary pipe work to join it to the filter system. You will still need the same size of pump, filter and UV. If you decide on a gravity fed system then you have a lot more options and choices with the water return.

So, let’s look at these two choices in a bit more in depth.

Pump fed filters

PumpIf you choose a pump fed filter system, the water is pumped from a pump situated on the floor of the pond, through the UV unit and into the filter, and then returns back to the pond directly or down a waterfall. Pump inlets will occasionally need to be cleaned and have any trapped particles removed from them. This will mean heaving the pump from the bottom of the pond causing disturbance. There is also the danger of small fish fry being caught in the pump inlet. However, there is no construction involved, simply connect your pump to flexible hose, drop it into the deepest part of the pond and connect the other end of the hose to your filter inlet.
The outlet from a box filter is usually bigger than the inlet, this is so it doesn’t overflow. This is connected to return pipework which is gravity fed back to the pond either directly or via a waterfall or header pond.

Gravity fed filters

A gravity fed koi pond filter system is however without doubt the best way to run and maintain a large koi pond. A bottom drain is fitted into the bottom of the pond at the deepest point. This means that all solid waste is directed to the drain. The drain has a grille cover and water flows by gravity through the drain into 4” / 110mm pipe work which then connects to the filter inlet.

You do need to ensure that the height of the surface level in your pond is set to the same height as the height of the filter water level, otherwise your system will not work.

This will then feed into the first chamber of the filter, unless a vortex chamber is fitted which acts as a settlement chamber. This traps most solid matter coming from the pond, which can be flushed to waste. It is best to fit a gate valve between the filter and the pond’s bottom drain so that it can be shut off during any maintenance.

Water enters the filter and passes through various chambers containing different filter media. The first chamber is often filled with filter brushes, which stop bigger particles from going any further. Other chambers will consist of media such as filter mats, flo-cor,  k1, alfa grog,  volcanic rock, bac-bio balls, bio-flobac tubes, zeolite, ceramic media or filter pads.

The last chamber will consist of a submersible pump which pumps the water back to the pond. Alternatively you can fit an external or dry pump outside of the filter chambers.

Other considerations

Whether you are using a gravity or pump fed filtration system, you may also wish to fit a venturi. This is fitted inside the pond and the return water feed is passed through it. As it does so, air is drawn in through a vertical pipe and mixed with the returning water. This places aerated water back into the pond, something which your koi will appreciate in those warmer summer months. If this is not added, you may wish to consider installing an air pump, air line and air stone, which will of course add to your running costs.

SkimmerThere are many other equipment additions you may wish to add such as pond skimmers, pond heaters, pond sieves, pond lights, air pumps and air stones, waterfalls, blanket weed removers…. The list goes on and on.

However, apart from skimmers, these can be added at a later date and are not essential during the initial build phases. Just make sure that if you do want to add more electrical items at a later date, plenty of electrical points are provided for in the initial stages. And do always get someone who knows what they are doing to install electrical appliances.

When using electrical equipment, it is best to house switches and the like in a suitable place near to the pond and run one supply into this. Use a pond safe switch box. These are individually fused and have neon lights to show that everything is working properly. You should also fit a trip switches onto the feeds to any electrical appliances.

Extra bits and pieces you may need.

Koi safe nets. Make sure that your nets are suitable for handling large koi. This means fine soft mesh. A separate net or nets may be useful for removing debris from the pond.

Tap Water Conditioner - for removing chlorine and toxins from tap water.

Filter Starter - to help boost the helpful bacteria in your new filter.

Test Kits - to periodically check the levels of ammonia, nitrite and pH in the pond water.

Fish Food - always buy good quality foods for your fish, cheap food is no good for your fish, your filters or your water quality.

Koi Viewing Bowls – for treating of sick fish separately from the pond and other fish.


Our next section deals with building your koi pond, or if you would prefer, you can return to the pond design page.

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