Keith Holmes says...

See issue 132, Q&A in-depth for Keith's complete answer on building and installing an economical Koi pond.

Final figures for a pond build (12ft x 8ft x 5ft; 3,000 gallons)
Pond build (excavation, blocks, concrete base, and insulation): £2,000 if doing the work yourself, more if using a builder.
If you need to get skips to remove soil you could easily add another £1,000 to this.
Box-welded liner: approx £500
4in drain: £19.95
4in slide valve: £49.95
Skimmer: £40
Pipework and glue allowance: £200
 
Five-bay multichamber with vortex: £600 (approx)
Aquamax Eco 12000: £279.95
TMC 55W UV unit: £145
KP1 purifier: £120
Bubble cover: £105.00
Dura 6 heat pump: £1,400
Koi air 50: £94.95
9in air disc: £29.95

Total: £5584.75 (using higher end approximations.) – with building work being undertaken by pond owner and using excavated soil to avoid skip costs.

Optional extra MultiCyclone: £295
 

Peter May says...

Bedding plants are always the nation’s favourite when it comes to adding colour to bland gaps, while an otherwise sparsely planted shrub or herbaceous border gets established. However, unless you grow them yourself from seed they can prove an expensive stopgap. These plants are often the half-hardy annuals listed in the seed catalogues and therefore not tolerant of frost. Petunias, begonias, nicotianas, marigolds and geraniums are all the types of plants you could start from seed or buy to plant out in your own garden once the threat of frosts have subsided. If your garden is relatively slug and snail free, a more economic option at the right time of year would be to sow packets of annual seed straight into the ground. These are the plants listed as hardy annuals, ranging from Larkspur, Californian poppies, poached-egg plant, nasturtiums, nigella, sunflowers and many more.
 

Peter May says...

Vegetable filters or simple reed bed systems are an ideal supplement to any pond that has a high pollution potential or a large population of fish. Although most biological filters can process the waste from fish into nitrates, it is getting rid of those nitrates that most systems have difficulties with. This is easily done by the micro-flora around the roots of higher plants. Just planting up a stream or the header pools in a waterfall system can be beneficial, or even planting up the surface of your existing biological filter is better than nothing. A purpose-planted container where the polluted water rises up through a porous planting medium, or gravel planted with fast-growing water plants is ideal. The best plant for this job is the cheapest, and it also grows quickly: the common or Norfolk reed (Phragmites australis). You will need a submersible pump capable of handling solids and pumping the complete volume of the pond water every two hours, 24/7 to the top of the filter bed. If you are incorporating this with an existing biological filter you already have the most expensive equipment. All you need to do is run the filtered water through a gravel bed planted with common reed. Plant it no more than 20cm apart straight into the gravel or leave it in aquatic baskets for easy maintenance. The beds need be no deeper than 25cm, with a total surface area of no more than one third of the pond’s surface area.
 

Peter May says...

All pond life needs oxygen, including at the bacterial level. But oxygen does not dissolve readily in water and in order to increase this potential it is necessary to expose as much of a surface area of the water as possible to the oxygen. Any process that moves water about in the open air gives it the chance to absorb a little of the oxygen in the atmosphere. This can be done by creating droplets from a fine fountain, which must be the most cost-effective method of achieving oxygenation. Unfortunately, fine fountains are at the mercy of wind and local turbulence, casting the water adrift from the pond. There are styles of fountain jet that use energy from a pump to suck water and mix in air at the same time. These gushing, frothing jets send up a column of white water that is as much a mixture of air and water as you can get. Because of the strength and volume of the column of water, the jet is less prone to being blown by the wind. Waterfalls are also good, especially those that splash water about. You may feel that you have enough oxygenating plants in the pond to sustain the biology of the pond during the day, but at night, when oxygenators stop oxygenating, you need an extra supply to sustain the fish and the bacteria. However, if you run an extra oxygen supply night after night, the pond environment will get used to it. Soon the wildlife and bacteria in your pond will need it all the time.
 

Peter May says...

Koi are naturally curious and equipped to grub around in mud and soil; they are even strong enough to tip over large aquatic baskets. They do however benefit hugely from the natural balance that a full quota of plants undeniably brings. The daytime oxygenation from submerged aquatics is beneficial, as is the uptake of unwanted chemicals by all water plants, particularly nitrates, which is difficult to achieve with anything but the most sophisticated filtration equipment. However, for many serious Koi keepers, leaving water management and oxygenation to nature is to tempt fate and lose control. There are others who claim to have had no problems. This may be because they have particularly well-established ponds, or they introduced the fish when they were small. You can try planting in aquatic baskets as normal, but even if you use the fine-meshed ‘Finofoil’ baskets, line them with some underlay or a hessian square to keep the fine silt in the basket; use a heavy, chemically inert gravel (20mm minimum) on the surface. You could start oxygenating plants and lilies off in a ‘quarantine area’, or try a vegetable filter or reed bed system so the plants can do their job away from the fish.

Peter May says...

Laburnum and yew have to be at the top of the danger list of trees, since every part, including the pollen, is poisonous. Alder buckthorn also has poisonous leaves, bark and berries. Any tree that sheds foliage or berries into the pond is liable to overload the biological filter system, but the leaves of willow contain salicylic acid – the basic ingredient of aspirin, which is highly poisonous to fish. Oak leaves contain tannin, which in large volume can also be poisonous. Smaller trees and large shrubs include the guelder rose (Viburnum opulus) that is poisonous in all its parts, and to a lesser extent the rhododendrons, oleanders, wood spurges and daphnes. Holly berries can be poisonous in quantity. I have always been told to avoid planting elder near ponds, but cannot find any written evidence for avoiding it. Dodgy climbers include the wisteria, the solanums (avoid all members of the potato and nightshade family) and  honeysuckle and sweet peas, all of which have poisonous berries and seeds. If you let ivies flower and seed, these too can be poisonous in quantity. Large perennials often found in boggy regions may cause problems and include the giant hogweed, foxgloves and larkspur. Even bluebells and hellebores are best avoided.

Keith Holmes

Use the following calculation:

Length + (depth x 2) + required overlap = total length of liner required

Width + (depth x 2) + required overlap = total width of liner required

If your hole is 10ft long by 8ft wide by 6ft deep and you need an overlap of 6in all the way around, your liner should be:

Length = 10ft + (6ft x 2 = 12ft) + 1ft (6in overlap each side) = 23ft long

Width = 8ft + (6ft x 2 = 12ft) + 1ft (6in overlap each side) = 21ft wide

If your pond has ledges, or an uneven bottom, take a direct measurement. Lay a piece of string or long rope tape measure down one side of the pond, along the bottom, then up the next side. This will give you the exact measurement for the amount of liner required.

Keith Holmes says...

Firstly, you need to consider the size of pond that you hope to end up with, then discuss with your local Koi dealer the area required for all of the associated equipment. Before you make a final decision you should also consider:

1 Access: Is there easy access for skips, diggers and machinery?

2 Utilities: A Koi pond will require access to electricity, water, and maybe even gas. These can all prove costly to have installed if they are not already located close to where you propose to build the pond.

3 Trees: Are there any large trees or other well-established plants nearby? They may have strong roots that can cause problems with excavation or more serious problems to the structure of the pond once it’s built. Autumn leaves may also fall into your pond increasing the levels of maintenance required on your part.

4 Underground services: You may want to check the locations of underground pipes and cables. Too many times people have started digging only to end up drenched in water as they have gone through a
water main.

5 Proximity to buildings: Unless you are seeking professional advice from a suitably qualified person, always try and avoid locating your pond next to existing buildings for fear of undermining the integrity of that building.

6 Distance away from buildings: If you never use part of your garden now, will you use it just because you build a Koi pond there?

 Keith Holmes

There are three choices: liner, waterproofing paint or fibreglass. If you decide to use a liner to seal your pond you will be presented with a vast array at different prices, thicknesses, and with varying guarantees. As a rule of thumb, you do get what you pay for, and although you may be able to save yourself a considerable amount of money by using a PVC liner over a butyl one, in the long-term you may spend more getting it repaired. Liner is cheap and easy to install, but if your pond is an unusual shape you may find it takes you a little longer. You can buy a product called cold glue tape, which can be used to stick the creases down in awkward corners. If you have a pond with a more uniform shape you may want to consider a box-welded liner, which will cost you a bit more, but will be tailored to fit.

One of the most common pond paints is G4. As with any sealing paint, it is vitally important to ensure that a good smooth render is applied first. It is the actual structure and render that provides both the strength and appearance of the final finish, so it is worth spending a considerable amount of time getting these right. You may want to consider adding a product such as fibre mix to add strength to the render. It is vital that you leave the pond to dry before you apply the sealant. In some cases a drying period of three to four weeks may be required, so a good cover and protection from the elements is essential.

Fibreglass is considered by most to be the best pond liner after paint, but it is also the most expensive. A good rendered structure should be prepared and allowed to dry before any attempt is made at fibreglassing. Unless you’re experienced, it is better to seek the help of a professional fibreglassing company and preferably one that specialises in ponds. Always ask for references and, if possible, try and visit a pond to inspect the quality of their finish first-hand. Finally, do not be swayed by price; although there are bargains to be found, always ask what materials are being used, and actually check what you are getting for your money.

Keith Holmes says...

A bottom drain is an essential piece of equipment for a Koi pond as it allows for the continual removal of waste from the pond to the filter system. The best way to use a bottom drain is for supplying a gravity-fed filter system. The alternative is to use it as a means of dumping the pond water to waste periodically, but this results in any debris that has collected only being removed when the drain valve is opened. The problem with bottom drains is that they are very difficult to install in an existing pond. To install a bottom drain correctly, the drain unit (a 4in or 110mm pipe connected to a drain sump, if the pond is in excess of 1,000 gallons) needs to be installed in a concrete base, and to make this possible in an existing pond you need to empty the whole pond, remove the existing lining material and lay a new base, incorporating the new drain. If you already have a pond that was built without a bottom drain, which does not have gravity-fed filters, install a mid-feed through the side wall of the pond. A side feed should be positioned as low as possible and should be 4in (110mm) in diameter. Once installed you can use an elbow and a length of pipe to lower it to the bottom of the pond. It is best to use a side feed for a gravity-fed filter system, which will result in a certain amount of waste material being pulled from the bottom of the pond into the filters. A bottom drain is essential for a new pond; allow one per 4,000 gallons of water. Each drain should be located centrally and the base of the pond should be benched towards them. If you need more than one, divide the pond up into zones and repeat this process for each zone.

Keith Holmes says...

To work out the gallonage of a square or rectangular pond:

In feet and inches: length x width x depth x 6.25 = gallons

For example, a pond that is 10ft long by 8ft wide by 5ft deep would have: 10 x 8 x 5 x 6.25 = 2,500 gallons 

In metres: length x width x depth = m³ (1m³ = 220 gallons or 1,000l)

For example, a pond that is 2.5m long by 2.5m wide x 1.5m deep = 9.38m³; 9.38 x 220 = 2,064 gallons 

To work out the gallonage of a circular pond:

 In feet and inches: π (3.14) x radius (half the diameter) squared x depth x 6.25 = gallons

 For example, a pond with a diameter of 10ft will have a radius of 5ft; if the pond is 5ft deep, the gallonage is: 3.14 x 5m² x 5 = 392.50. 392.50 x 6.25 =
2,453 gallons 

In metres: π (3.14) x radius squared x

depth = m³

For example, a pond with a diameter of 3m would have a radius of 1.5m; if the pond is 1.5m deep the gallonage would be: 3.14 x 1.5m² x 1.5m = 10.6m³. 10.6 x 220 = 2,332 gallons

If you want to work out these figures in litres, one gallon is equal to 4.54609l.
If your pond is an unusual shape or has varying levels of depth, draw it onto graph paper, and then divide it up into zones that have equal depth or are of a more uniform shape. Having done this, apply the formulas shown to work out the gallonage of each zone, then add them all together to give you the total gallonage.

Ian Wellby says...

There are some good general rules. I believe the most important point is to buy fish you like. After that, look for the fittest, healthiest looking individual. Do not buy fish from tanks where there are sick-looking fish. Only buy from reputable dealers and get advice and recommendations from the BKKS and friends who buy Koi. I also tend to stick to one or two dealers that I know and trust. There are some extra rules for buying really good quality Koi. Start by looking for the qualities that indicate this is going to be a very good Koi; the fish should be full-bodied with large, perfect fins. A chubby-cheeked face is also a feature that is becoming sought after. The colour on the fish should be deep with sharp boundaries between colour blocks, and these should be large, regular and well defined. Interesting features such as coloured lips (kuchibeni) are a bonus.

Ian Wellby says...

The purpose of quarantine is to establish whether the new fish has a disease, which could adversely affect the resident fish. Any diseases that do show up can then be more easily treated in a quarantine system and will not spread to the resident population. It also gets the fish used to the conditions prevalent in your area. The fish should be kept in quarantine for at least two weeks and up to three months, preferably including some of the warmer spring and summer months. If this is not possible, heat the quarantine tank for a period up to 20˚C and then let it settle back to ambient temperature. This will help bring out any diseases that might be present. Every fish you put into your pond must be quarantined. The quarantine system should be large enough and have suitable filtration. If possible it should initially be filled with water from the pond and any water changes should be completed using pond water. All equipment (nets and buckets) should only be used within the quarantine system; colour code them with yellow electrical tape so there are no mistakes. Finally, it is a good idea to quarantine new fish with resident fish. If one or two resident fish are put in the quarantine system, not only will they keep the filters ticking over, but they will also react quickly to any nasty disease that the new fish have brought in. The quarantine the fish undergo at the dealer’s premises will not match your requirements, but it is good practice on the part of the dealer.

Ian Wellby

Rules for feeding include:

• Once temperatures are consistent at below 10˚C in winter you should
  stop feeding.
• Do not start feeding again in spring until the temperatures are steady above 10˚C. Then start feeding with a high protein diet.
• During the summer provide a variety of high protein growth diets.
• As the fish move through autumn (below 14˚C), switch onto diets that contain wheatgerm and are lower in protein.
• Koi are omnivorous and graze continuously; they should therefore be fed little and often.
• Judge the amount of food you give your Koi by what they will eat in five minutes. Then feed at least two or three times a day.

 It is also good to feed a variety of diets mixed together; store food in a dry, cool, dark place; do not use food that is older than six months; and do not use food that has been wet. Finally, give your Koi treats such as worms, blanched lettuce or prawns. 

 Ian Wellby

Certainly you should leave your fish where they are. I would advise that you ask someone you know and trust to come and look in on your Koi at least once every other day. If your pond is set up properly then all they need to do is to check the filter is still running and your fish are looking happy. Leave some food for them to hand feed to check the fish are coming up for food. When you are away it is advisable to continue the normal feeding regime as far as possible, but at half rations. You can buy automatic feeders that can be programmed to feed your fish while you’re away. While these are a good idea, they do not check to see if your fish are okay before feeding them, so you still need someone to have a quick look to see if everything is as it should be. You should also leave some instructions as to what to do if there is a problem. These should be simple and include advice on when to stop feeding, how to turn off automatic feeders and how to carry out a 15 per cent water change. Also, leave a contact number in case of emergencies.

 Ian Wellby

The guidelines for initial stocking of a Koi pond are 2in of fish per 1ft² (5cm per 0.1m²) of surface area. This will allow the fish room to grow. For example, if your pond was 6ft by 4ft then you would have a surface area of 24ft². You could therefore stock 48in of fish in this pond. The most important factor to consider for a pond is depth. To be able to keep Koi your pond must be a minimum of 4ft deep across some of the depth; this is to maintain an area of warmer water (4˚C) during the winter and to ensure the pond does not freeze completely. The minimum volume a Koi pond should be is about 330 gallons (1,500l). It is also important that the pond has some sort of filter system, unless it is really large and natural. There are a few other golden rules for stocking a Koi pond that you should always follow:

• Add stock slowly so the filter can get used to the new level of stocking and the increase in waste production.
• Fish grow, and Koi can grow very quickly indeed.
• Check the water quality frequently for the first few weeks after adding new fish.

 Bernice Brewster

If a parasitic infection is suspected, you should take samples of mucus from several individual Koi and examine them under the microscope. If it is necessary to hunt around the slide sample, or there are just one or two parasites visible, treatment is unnecessary. On looking down the microscope, if you immediately see obvious numbers of any parasite, you should undertake treatment. Consider the use of a proprietary treatment, carefully following the manufacturer’s directions and always completing the course. Once the treatment is complete, it is advisable to randomly check mucus samples from the Koi to ensure it was successful. Be aware that infections of flukes and Trichodina are evidence of a hygiene problem. Their presence indicates a problem with the filter system, as these parasites thrive where there is minute organic material in suspension in
the water.

Bernice Brewster

Basically, any factor that affects Koi in such a way as to extend or disturb the ‘normal’ resting condition. This definition includes just about everything, from water conditions, to netting and handling Koi, to predators. We tend to think of stress as very negative, but of course this response is a normal reaction. It is only when we prolong exposure to the stressful event that secondary disease problems can arise.

Bernice Brewster

Koi will flick and flash when something is irritating them. One of the reasons why Koi behave in this way can be due to poor water quality, most often due to the presence of nitrite, which is a skin irritant. Other chemicals dissolved in the water, such as chlorine, can also cause Koi to flick and flash. It is always worth eliminating water quality problems as the cause before pursuing any other course of action. Parasites, and occasionally bacterial skin infections, can also cause Koi to flick and flash. Those that cause irritation are visible to the naked eye, such as fish lice or even leeches, but there are also others, which are only visible under the microscope. If the irritation is due to poor water conditions, then regular, partial water changes are necessary until there is no nitrite left. Parasite infections can be treated using a proprietary medication, but be certain to follow the directions carefully and complete the course of treatment. If no parasites can be identified, but the Koi are still irritable, seek professional guidance.

Bernice Brewster

There are two elements that make up a Koi’s immune system. The first is non-specific immunity, which mops up any foreign body it encounters. The second part is the specific immune system. Here the cells of the immune system ‘recognise’ pathogens and cause a chain reaction of white blood cells to flood the infected area. The immune system is costly in terms of available energy and so the specific immune system is largely suppressed in the winter. The non-specific immune system runs continuously; no animal could afford to be completely vulnerable to any bugs looking for an opportunity to infect it. Spawning also affects immunity. Reproduction is the most important function over and above everything else and, as a consequence, the hormones that govern reproduction also suppress the immune system. Apart from natural causes, the other significant immunosuppressant is stress.

Bernice Brewster says

Carp pox, or more correctly fish pox, is caused by a herpes virus, the same group of viruses that cause cold sores in humans. The virus attacks the fine layer of outer skin, infecting the cells and making them produce more virus particles instead of mucus. The response of a Koi to infection with the virus is to produce more cells, which are seen on the body surface as white lumps with a waxy appearance. By the time these waxy lumps are visible, the viral infection has already subsided. It is important to realise, despite all the advances of the twenty-first century, that we still have no cures for viral infections. On the whole, fish pox is not particularly harmful to Koi and therefore the best treatment is to leave it alone. In the past it was advocated to scrape the waxy lumps off, but this damages the skin, leaving it open to secondary infections that are often more harmful than the original infection. Fish pox usually disappears in summer when water temperatures rise.

Bernice Brewster

There is much truth in the adage, ‘if it ain’t broke, don’t fix it’. We tend to have a warm, cosy feeling about all the treatments we add to a pond and, to be blunt about it, the coloured water often makes us feel better. But, it may not necessarily make the Koi feel well. In the same way that any medicine we take can have unpleasant side effects, most certainly Koi treatments do as well. Some of the medications we use are actually significantly poisonous and overuse can cause long-term, harmful effects. The short answer to the question is definitely no, preventative medication is not a good idea. Regular monitoring of water quality is essential and, in the summer months, increased aeration to the pond is also important. Many problems that arise with Koi health are due to inadequate dissolved oxygen concentration through the summer. Offer good quality feed to the Koi, and in the summer feed little and often. Most of us are probably guilty of not actually feeding adequately at this time of year.

Ben Helm says...

A crucial element in pond design is to ensure that the water within a pond circulates though the pond and into the filter at least once every two hours. This means that both the dissolved and particulate pollutants are carried to the filter on a regular basis, leaving the pond free of pollutants and debris. A dead spot is an area of a pond where, due to the flow characteristics within that pond, debris is allowed to settle a accumulate. Settled debris on the pond bottom is indicative of a dead spot and will require you to adjust the flow patterns so that all debris is either taken to the bottom drain or pump so that it can be removed by the filter. Dead spots are best prevented at the design and construction stage, removing any nooks and sharp bends from the pond's design, ensuring that sides and curves are sweeping and that the pond bottom slopes down to the bottom drain(s). The installation of a turbo bottom drain can help remove dead spots in other areas of your pond by sweeping debris into the bottom drain.

Ben Helm says...

Installing a suitably-sized UV unit is a guaranteed way of creating clear water in a pond. It works by causing the single-celled microscopic algae cells to clump together into larger particles that can then be removed by mechanical filtration. Anyone who has retro-fitted a UV unit to a pond will have noticed the sudden increase in debris (flocculated algae) that a UV unit can create. Algae (green water) blooms in a pond as a result of there being a high nutrient (nitrate and phosphate) content in the water and therefore addresses the symptom rather than the cause. Consequently, when the UV unit has created a crystal-clear pond that is still high in nutrients, in moves blanketweed to capitalise on these growing conditions. A UV unit will not eradicate blanketweed as it does not pass under the radiation of the lamp, but remains and grows within the pond.

Ben Helm says...

It's difficult to give a definitive answer to this question. In the same way that there are guidelines for how many fish should be stocked per unit area of pond, there are formulae that can be used to calculate the size of biofilter needs to be effective. I think I can remember only using such a formula once, and have not done since. The difficulty in being so precise with such a question is that there are so many variables than can and will change, and these are also difficult to measure accurately. Factors that will determine the size of filter required include temperature, flow rate, pond volume, stocking density, age of fish, food type and quantity, choice of media and contact time. There are also several rules of thumb, such as the surface area of the media should be 20% to 30% of the surface area of the pond, but is that using pea gravel or sintered glass? Do you see the problem?

I suggest that years of industry experience are best applied when answering this question and that you should research the different pre-fabricated filters, including the media that is used, and note the size of pond that each filter is rated at. If building your own, do not go any smaller than the ones you see for sale. With regards to the proportion of mechanical to biological, experience show that the limiting factor of a filter is usually the mechanical side, recognising that the surfaces within the pond itself will add to the pond's biological activity. The mechanical area should equal, and at best exceed the biological area (if using settlement). This rule of course does not apply if using an active means of mechanical filtration such as screens or meshes. 

 Ben Helm says...

These two terms are taken from a filter's perspective. A pump-fed filter is probably the most widely used in smaller ponds. Driven by a submersible pump situated within the pond, the filter is situated outside and above the pond as literally pump fed water from the pond under pressure. Typically, the water within a pump-fed filter will trickle down through the media (although sealed, pressurised units are available) and return to the pond by gravity, usually feeding a waterfall. A gravity-fed filter is situated adjacent to the pond, at the same level. Fed by a bottom drain, a gravity-fed filter will usually be multi-chambered, with the final chamber housing the pump, which returns the water under pressure to the pond (often via a venturi). Consequently, the pond's surface will always be slightly higher than that in the filter, making water pass through to the filter via the bottom drain under gravity.

Ben Helm says...

The best time to service or clean a filter is when the Koi are at their least active in the pond, and therefore least dependent on the filter's funtion – early spring or late autumn. Unfortunately, this is also when the filter is less likely to need regular maintenance. When Koi start to feed more actively you will also have to clean out the mechanical chambers (or media in a pump-fed filter) more frequently. For a pump-fed filter, where the media usually doubles as both mechanical and biological and is exposed to the relatively oxygen-rich air, this is not a problem as long as it is cleaned in pond water. In a gravity-fed filter, mechanical chambers can be purged independently of the precious media in the biochambers, enabling you to preserve your filter's maturity. In the warmer months when bacteria are more active, and when the water holds less oxygen, this should be carried out as quickly as possible. The addition of airstones in the biochambers will reduce any adverse impact this short period of downtime may have on your filter's performance.

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 Peter May says...

Peter May says...

In general they cannot, but there are some Koi keepers who manage to get the balance just right and their Koi and plants live together in perfect harmony. I know of a pond Pembrokeshire where there are plants galore – but the plants are pristine and the water is crystal clear. It is equivalent to 'green fingers' in gardening where some Koi keepers just have 'the knack.'

 Ben Helm says...

Despite their premium status as a pond fish, other pond fish will easily live with Koi as they require similar pond conditions and diet. This means, for example, that goldfish will easily live in a Koi pond, whereas the opposite is not ideal for Koi due to the size of the pond and filtration required.

 Keith Holmes says...

At water temperatures of below 5C (42F) your Koi will be at risk from the cold water and death may occur. At the other end of the scale, when pond water temperatures reach 28C (83F) and above oxygen levels will fall and leave your Koi exposed to very low oxygen levels which, once again, may cause death.

 Bernice Brewster says...

Water temperature influences food requirements; in cold winter weather Koi move very little and body functions are reduced to a minimum so they are using little energy and can go for two or three months without eating. In warm summer weather, Koi should not be deprived of food unless they are being transported.

Ian Wellby says...

They are known as detritivores, which means they will pretty much eat anything. This will include insects and crustaceans, which they eat routinely, but they will only very rarely eat small fish. They eat a lot of vegetation and also rotting organic matter from the silt on the bottom of a pond.

 Bernice Brewster says...

Koi grow all their lives but the growth rate slows down once they become sexually mature. However, they can exceed a metre in length providing the water quality in the pond is excellent and they are fed appropriately.

 Keith Holmes says...

You can build a cheap Koi pond but the chances are that it will come back to haunt you. If you are on a budget you are better off building a smaller pond with good equipment than building a larger pond and having to scrimp and save on the equipment you use. Alternatively, you could continue saving until you have the budget to build and equip the pond of your dreams.

 Ben Helm says...

As a non-native fish, Koi should not be found in the wild, nor should they ever be released into our native waters (it is an offence to do so). Some privately owned enclosed fisheries do stock Koi and ghost Koi as an ornamental alternative for anglers to catch.

Ben Helm says...

Koi can easily live for 20-30 years in a pond, with specimens in Japan reputedly living for over 200 years. Their lifespan is seemingly determined by a complex combination of genetics, husbandry and the quality of an environment. 

Ian says...

Yes. The goldfish x carp 'hybrid' that is produced is a relatively common hybrid and can occur, even in the wild.