Koi Pond Requirements

KOI POND REQUIREMENTS -- Koi Fish can grow in big size to 80 cm or 100 cm. Koi Keepers must accomodate this potential size with large koi pond. Koi ponds come in many shapes and sizes, from the relatively modest sized pond that may hold a mixed collection of koi carp and Goldfish, through to ponds of many thousands of gallons. A pond of around 8 feet x 6 feet and 4 feet deep (2.5m x 2m x 1.2m) containing approx' 1200 gallons (5500L) would be a sensible minimum for keeping Koi in the UK or other temperate climates.

Koi Pond Size

The larger the volume of water the more stable the pond will be. A hot day can send the temperature soaring in a small pond, whilst a cold night can see it plummet. Fish are cold blooded and their body temperature matches the temperature of the pond. Sudden changes in temperature will cause physical stress and may lead to disease. This also applies to Goldfish and other pond fish. But Koi carp have been progressively interbred over many years to develop their colours and like most pedigree animals are relatively delicate. For this reason they may develop health problems in conditions where Goldfish are living quite happily.

The stability of the water temperature is also greatly affected by the ratio of surface area to volume. The larger the area in relation to the depth the greater the affect of sudden changes in air temperature, if you have two ponds with the same volume but one is deeper than the other it will be less affected by temperature fluctuations.

Koi Pond Construction

As well as considering the size of the pond, it is worth spending a little time considering the shape and construction method. Ponds with simple shapes and flowing curves allow a good circulation of water and avoid dead spots. Construction in concrete blocks, with a rendered surface and finished in fibre glass allow for the rounding off of corners in a rectangular and sloping of the pond base towards the bottom drains.

This method of construction is the most expensive but gives the best results. Care should be taken to make sure the type of final gel coat used with the fibre glass will completely cure and not leach styrene into the water with potentially fatal results for your Koi. There are a number of specialist fibre glass firms that will undertake this work and a firm that has experience of building Koi ponds will ensure the correct finish is used.

A cheaper alternative and probably the most commonly used method of building Koi and Gold fish ponds is to use a good quality rubber pond liner.
To calculate the size of liner required, measure the longest distance across the pond and add twice the maximum depth to obtain the length. Measure across the widest point and add twice the maximum depth to obtain the width. Then add a foot (30cm) to each measurement to allow for an overlap. So for a pond of 8 feet x 6 feet x 4 feet deep the liner would need to be 8 + (2 x 4) + 1 = 17 feet long and 6 + (2 x 4) + 1 = 15 feet wide.

When fitting the liner, care should be taken to pleat and fold the corners carefully to minimise the chances of debris becoming trapped. The corners can be fixed down flat with special mastic tape to give a good finish.

Koi Pond Filtration

After settling on the size of your Koi pond, the next step is to ensure good filtration. Koi produce large amounts of solid waste, so your ponds' filter system must have good mechanical filtration to remove solids from the water.

The mechanical filter can be in the form of nylon brushes, plastic media or a vortex that slowly spins the water and allows larger, heavier particles to settle out. The mechanical filter must be easy to clean and if it is fed from a bottom drain must have a valve to shut it off from the pond for regular cleaning.
 It is recommended to clean this section on at least a weekly basis. A good gravity fed filter system will incorporate a drain for easy flushing to waste and this can be used to carry out regular water changes.

Biological filtration is the next step, a biological filter utilises bacteria to break down the ammonia produced as a by-product of the fishes' metabolism. The bacteria live on the surfaces of the filter media and break down the Ammonia excreted by your fish. To be blunt your lovely Koi pond is just a giant toilet bowl for your Koi .Unless the Biological filter breaks down the waste produced, your Koi will succumb to illness or be poisoned by the waste. Ammonia is broken down firstly to Nitrite and then to Nitrate, which is relatively harmless to Koi and other pond fish. The level of Nitrate is kept under control by regular small water changes.

Please remember that it takes a minimum of five to six weeks for the bacteria in the filter to build up. During this period, only a few fish should be introduced and the amount of food kept to a minimum. It will probably take several months for the filter to fully mature. Water can be fed into the filter system either by a pump or by a drain in the bottom of the pond.

Most modern Koi ponds use a bottom drain and this has the considerable advantage of delivering solid waste to the filter system in an intact state, where it can be more easily settled and removed from the pond. This is called a gravity fed filter system and unless there is some particular reason why one cannot be installed, we recommend this as the best method of filtering Koi ponds