Pond fish keeping advice information

The popularity and growth of the koi and pond keeping hobby is largely due to it being accessible to a wide range of aspiring pond owners, irrespective of their time, budget or space.

Koi keeping has suffered from the label of being a pastime of the rich and famous and that a pond full of koi is the privilege of the pop star or tycoon. In many respects it has been this lure as a status symbol that has witnessed many image conscious individuals to enter the hobby overnight by investing 6 figure sums in a pond and its inhabitants, only to leave the hobby some time later just as quickly.

In contrast, thousands of people are bitten by the koi bug each year and many prove how successful and fulfilling koi keeping can be on a sensible budget. Typically, a few hundred pounds and an aptitude for DIY are sufficient to start on the road to successful koi keeping. A lucky few also enter the hobby each year and are able to commission professionals to design and install their koi pond for them, intent on achieving koi Nirvana at the first attempt. Neither of the two scenarios are right or wrong in their approach, but are rather evidence that koi keeping can be extremely accessible to a range of budgets. However, the ‘beginner’, ‘improver’ or ‘ultimate’ koi keeper will have different items on their shopping lists.


For those people planning a koi pond, there are 5 essential items that must be purchased to achieve a ‘no-frills’ but successful koi pond. The beginner is regarded as having a limited budget but one who is willing to invest in quality equipment that will outlast and outperform some cheaper alternatives.

1. Pond liner.

Pond liner is available in a range of materials or composites of different flexible materials. The two essentially different types of liner are uPVC and butyl.

Each of these materials will carry a similar guarantee of 25 years with uPVC liners typically being less expensive than the butyl. Liners are bought off the roll with a wider range of uPVC liners being commonly available.

Butyl liner is more flexible and is available in greater thicknesses than uPVC, however, if the excavated hole is prepared sufficiently well then either type of liner would suffice. Underlay is available for pond liner to protect against protrusive stones or roots but sand and old carpet are useful alternatives.

2. Filter

A filter is the means by which your koi are kept alive. It is bought to complement the size of a pond and installed at the same time as the pond liner. The simplest and most reliable way of obtaining an effective filter for a new pond is to buy a pre-fabricated filter. Depending on their design a pond filter will either be pump-fed or gravity-fed, the cheaper and easier to install being the pump-fed type.

Pump-fed or gravity-fed?

Pump-fed filter. A submersible pump sited in the pond pumps water from the pond into a filter which is positioned above the water level. The water runs through the filter and returns to the pond under gravity, often feeding a waterfall.

Gravity-fed: The filter sits alongside the pond and is buried to lie flush with the ground. It is connected to the pond via pipework (usually from a bottom drain and/or a surface skimmer). A pump in the final chamber returns the clean water directly into the pond. (End of Boxout)

A filter performs several roles as a life-support system.

Mechanical filtration. Particulate material that is pumped into a filter is removed by foam which traps the solid matter, allowing the cleaned water to flow into the remainder of the filter.

A filter also performs a biological function, detoxifying the poisonous waste products excreted by fish. Beneficial bacteria colonise the hard surfaces of the filter media, digesting and breaking down the soluble and invisible ammonia. A first group of bacteria break the ammonia down into less toxic nitrites which have a habit of proving to be more difficult to breakdown into relatively harmless nitrates, which can be removed by a water change, or through plant growth in the pond.

The biological function of the filter takes weeks or months to become established and during this time, the pond is most vulnerable to poor water quality. Care must be taken to monitor the water quality during this running-in period as koi stress and fatalities will soon occur during this time.

3. Test kits.

Test kits may often be overlooked as an essential piece of koi keeping equipment, but how else can you accurately determine the quality of your pond water?

As ammonia and nitrite are odourless and colourless, we must be able to test the state of pond water (especially when the pond is new) and address any problems immediately.

There are a host of test kits available to the koi keeper and at some considerable expense. However, there are 2 essential test kits, that can provide a snap shot of the health of the pond.

a. pH. A desirable range is between 7.5 and 9.0 (maximum). This range is the slightly alkaline pH that carp prefer and is also fortunately the pH of most tap water.

b. Nitrite. This tests the filter’s performance. If there is a nitrite reading, then too much ammonia is being produced relative to the bacteria’s capacity to break it down. This could be due to overstocking, overfeeding or more likely, an immature filter. A desirable nitrite reading is zero and if a positive nitrite reading occurs then carry out a 30% water change and resume feeding when nitrite returns to zero.

4. Pond pump.

If the detoxifying functions of the filter is regarded as the liver and kidneys of a pond, then the pump must be the heart. The majority of ponds are recirculated reliably by a submersible pump. Placed in the pond itself, a submersible pump will circulate water to the filter. It is run continuously, night and day, servicing the hungry bacteria in the filter with a regular supply of dirty water and soluble food.

A pump must be the most reliable piece of pond equipment as a pump failure can soon put your koi under real threat. Retailers will recommend the most suitable and reliable pump (ask them which pumps they use to circulate their ponds) with many leading pumps offering a 3 year guarantee.

In a similar way to the filter, a pump’s size is dictated by the capacity of the pond. Pump selection must take 2 factors into account. a. The pond volume b. The head the pump is required to pump. (Head = vertical distance from the surface of the water to the top of the discharge pipe). The higher the head, the lower the turnover of the pump and a pond’s volume should be recirculated at least once every 2 hours.

5. UV clarifier

Perhaps 15 years ago, a UVc would not have been considered an essential piece of pond equipment. However, pond keepers have received this innovation with open arms and a UVc is now widely regarded as an essential piece of pond equipment for guaranteeing clear water.

In a pump-fed system, a UVc is installed between the pump and the filter. A UVc is an ultraviolet light which makes the green water-causing algae to clump together. These clumps can then be removed by the filter leading to crystal clear water. The UV bulb will need replacing each season and is best done in spring time before green water begins to cause a problem.

The Improver

What can a koi keeper, who perhaps started as a beginner 2 or 3 years ago seek to add or improve to their system?

Filter improvements.

Filtration is the most widely debated topic of koi keeping with many different experiences leading to a diversity of opinions between suppliers, retailers and koi keepers. Filtration is also one of the most dynamic areas of the koi keeping hobby, with many innovations in media and design revealed to the hobby each year. The filter is the most likely part of a pond one would want to improve. What improvements can be made and are they justifiable?

1. Filter type.

Conversion from a pump-fed to a gravity-fed system. This will allow greater space for improved filtration, dividing the filter into a number of different chambers.

This is a major undertaking and would require the whole pond to be removed as a gravity-fed filter is best to be fed via a bottom drain. A bottom drain involves creating an opening on the pond bottom which is piped beneath the pond to the first chamber of the filter. This will also require the pond bottom to be reinforced with concrete. Quite an undertaking! The multichamber approach of a gravity-fed filter allows a great degree of versatility when choosing the function of each chamber and allows easier filter maintenance.

The majority of space should be set aside for settlement and entrapment of solids, perhaps using brushes to slow the water down.

2. New media

The biological chambers can be filled with a more efficient combination of media than simply biofoam. These could include Alfa grog, bio balls, flocor, bio-home and Japanese matting.

Buffering material could also be added to the final chamber to ensure that the pH does not fall below the desirable pH7.5. Buffering materials include: lime chippings, cockleshell and tufa rock.

3. Auto Top-up.

A handy auto top-up device can be installed quite easily to a gravity-fed filter. Water that is lost from the pond through evaporation or splashing will not go unnoticed by this easy-to-plumb device. This will even automatically top-up the remainder of the pond’s volume after a partial water change.

Other equipment to consider.

A more experienced and advanced koi keeper should also consider some of the following as they will benefit their all-round success by providing diverse sources of information.

4. Test Kits

A mature pond needs to be tested less regularly than when it was first installed but the parameters that are tested will differ from before. Test kits for nitrates and phosphates will be useful to detect how rapidly they collect and how frequently pond water needs to be changed.

5. Microscope.

A microscope is an excellent investment and would make a good birthday present – something that will prove to be useful throughout a koi keeper’s lifetime.

A microscope is straightforward to use and is the only way of positively identifying a number of external parasites. This will further your knowledge on koi diseases and enable you to target the pest more accurately with medication. It will also allow you to determine the efficacy of a treatment by taking a skin scrape after a course of medication.

6. Koi Society Club membership

This is a must for the dedicated Koi keeper. Membership will provide many benefits ranging from sharing in the experiences of other koi keepers to visiting other parts of the country on dealer or show visits. Regular meetings will also widen the perspective of any koi keeper, hearing presentations from other enthusiasts.

7. Subscribe to a magazine

A monthly subscription to a dedicated magazine such as KPG will also add to your knowledge and understanding an keep you informed of the latest trends. Packed with advice and promotions from dealers and brands, a magazine offers unrivalled, up-to-the-minute news and comment on the koi keeping world, home and abroad.

8. Additives

An extremely beneficial pond additive is a high quality montmorillonite clay. It is used by koi keepers who are willing to sacrifice a day or so of clear water in exchange for the benefits that their koi will receive from the minerals that are released into the water. This regular treatment attempts to mimic the ideal conditions of a mud pond, without sacrificing the crystal clear waters of the koi pond. Ultimately, clay dosing will lead to clearer water, improved skin quality, colour and vitality.

9. Handling Equipment.

A floating basket and inspection bowl are essential for the hands-on koi keeper. They are necessary for the effective taking of skin scrapes and topical treatment of wounds or ulcers. A sock net is also useful when handling or transferring koi between bowls. The finest of these nets will not only retain the fish, but also the water in which they were netted.

10. Air Pump

A pond air pump, capable of blowing air to the pressured depths of ponds is essential for the vitality of a pond and filter system. If fitted with suitably sized air diffusers, they will enhance the performance of a biofilter and the vitality of koi by increasing the dissolved oxygen content. An air pump also provides a pond with excellent back-up should the water pump fail and is essential in warmer growing months of summer.

The Ultimate

The ultimate koi keeping equipment will lead to the highest quality water management systems and deliver labour saving features, as well as adding the finishing touches to the image and appearance of the pond. These include:

1. Superior Construction.

The ultimate pond would be professionally constructed out of block work and fibreglass with a reinforced concrete base. Only built once, and built to last, this ultimate koi pond would be designed at least 6 feet deep with wide, sweeping sides, The blockwork and fibreglass construction will provide a robust and koi friendly environment that will show koi off in a stable and stress-free pond for many years to come.

2. Filtration

Improvements in koi pond filtration have seen a move towards the unconventional. Enhanced biological action can be achieved by incorporating a trickle tower filter. Positioned above the surface of the pond, the trickle tower provides excellent aerobic conditions for bacteria which are fed by a rotating spray bar. This above-ground construction can be difficult to camouflage.

A sand pressure filter can also be installed to an existing set up to polish the pond water even further. Borrowed from the world of swimming pools, it requires the power of a dedicated surface-mounted pump to pressurise the filter. It does, however, perform an excellent role and may prove to be too efficient, requiring regular back washing.

3. Surface Skimming

Water quality can be improved further by installing a surface-skimmer, which skims water from the pond surface, along with any debris or scum, maintaining a crystal-like surface to the water.

4. Air Dome

The performance of the bottom drain can also be enhanced by replacing the conventional dome with an air dome. The relentless stream of fine bubbles rising from the pond bottom not only aerates water from the pond bottom, but also mixes the water, pushing the settled debris into the bottom drain, adding a turbo action.

5. Protein Skimmer.

There can be a tendency for pond water to adopt a yellowish tinge as particular dissolved organic substances accumulate. Marine aquarists have been tackling this issue for years, by using protein skimmers, and similar units are available for the pond market, designed to remove these unsightly proteins from the water. They can be installed out of sight, and will enhance the water clarity and stability of any koi pond.

6. Heating

Perhaps one of the most sought after luxuries for the ultimate koi pond is a means of heating the water. This can prolong our interaction with koi through the harsh winter months, enabling us to monitor their progress rather than simply hope that they will survive through the winter.

Very briefly, these can be either gas fired or electric units and can be installed retrospectively. Being thermostatically controlled, they allow the water to be kept at temperatures that will allow koi to keep on feeding at a reduced level over winter, rather than experiencing a completely fallow period. There is however, the small issue of running costs!

7. Advanced Water Monitoring

Taking water testing a stage further, electronic means of water testing open up a further dimension of control. An electric Dissolved Oxygen meter can be set up to sound an alarm if levels drop below the desired limit. This can prove invaluable when wishing to salt or medicate your pond.

An extremely accurate way of measuring the true salinity of your pond is to use a refractometer. Highly accurate and easy to use, a refractometer will give a lifetime’s unerring service, even when measuring the very low levels of salt used in a koi pond.

8. Autofeeder

A real luxury and labour saving device for when you’re out at work all day is an auto feeder. Available in a range of specifications from clockwork to digitally controlled solar powered units, an auto feeder can dispense food regularly throughout the day. This allows koi to be fed how they prefer and keeps them active and inquisitive throughout the day.

9. Underwater vision

For another angle on your fish, why not keep tabs on their behaviour by installing an underwater camera. A permanent live link-up can, at the flick of a switch, provide you with an immediate update on you koi’s health, behaviour and activity.

10. Water Purification.

The quality of our drinking water seems to constantly be under scrutiny and is acknowledged as being less than fish-friendly. If possible, a dedicated supply of purified tap water should be used when filling or topping up a pond. A number of water purifiers are available and will remove a range of toxins, such as heavy metals and pesticides. Viewed less and less as a luxury, water purifiers are useful at guaranteeing the pond water’s suitability for fish.

11. Koi Software.

For the IT literate koi keeper, a number of koi management programs allow the logging of relevant water quality and environmental data and provide the koi keeper with a first port of call for diagnostic and disease information. However, like any data-based software, it is only as up to date as its latest entry, and requires regular inputs of information.

12 Tasty treats.

Besides providing top of the range artificial diets, that provide excellent growth and colour enhancing properties, a gratefully accepted treat is freshly defrosted mussels and shrimps. Although quite extravagant, they offer a source of high protein that is ingested whole, and will not cloud the water. They are an excellent food when conditioning broodstock.

13. Quarantine.

Behind the scenes, a precautionary system could be set up for quarantine purposes as a reception centre for newly acquired or ailing koi. Suitably sized and filtered to prevent stressing even the largest of koi on your shopping list, a quarantine facility is both the firewall and back-up facility required to maintain the ultimate koi collection.

14. Oriental Visit?

The ultimate koi keeper, not wishing to skimp on the whole objective of the koi pond may even consider a trip to Japan to hand pick a number of koi for their collection. Worth the investment for the opportunity to hand pick from myriads of top class koi, the visit will also live long in the memory for the many cultural experiences. It may even inspire you to create a complete Japanese theme for your garden complete with Bonsai, granite statues and eastern horticulture. Surely the finishing touch for the ultimate koi pond.

1. Best buys for first time koi builder: 1. 25 year liner (minimum) 2. A robust, reliable pump with a 3 year guarantee

Best budget buys:

1. Purchase or hire a video on pond installation. This will keep your mistakes to a minimum and allow superior DIY installation first time.

2. Use sand or old carpet as underlay for the liner.

3. Invite friends around for a koi pond digging party!

Best buys of secondary equipment

Look out for cheap filter media for your existing filter at the end of the pond season.

Bottom drain. Excellent way of providing unrivalled solids removal to a filter.

Auto top-up – an excellent concealed and labour-saving device, and easy to install.

Look around DIY centres for alternative materials to use in a Japanese hard landscape.

6. Keep your eyes pealed for a self-supporting tank that may work as a quarantine tank.

Best Medium Budget Buys:

1. Microscopes rarely deteriorate with age. Scan the second hand market for a good working model.

2. Clays. An inexpensive yet effective way of improving your koi’s health and vigour.

3.Don’t be tempted to buy ‘Japanese’ kit or consumable when a UK equivalent product will perform equally as well.

3. Best Buys at the top end of the budget

1. Air dome conversion to a bottom drain. Provides excellent aeration and mixing action.

Refractometer. An excellent investment in a truly accurate and scientific piece of equipment.

3. Blockwork and fibreglass construction. Unrivalled in durability and maintenance

How to avoid making expensive mistakes

Gathering information is the key to avoiding expensive mistakes. Hire or buy a video on pond construction and installation or join your local koi club or society. Members are quite happy to invite you to their ponds and to discuss the pitfalls and trade secrets when approaching such a mammoth project.

A reliable, patient and experienced koi dealer is also invaluable in guiding you through the practical minefields of plumbing, filtration and construction. A good rule of thumb is to find a dealer who would sooner see you leave their premises with good practical advice rather than a quick and unnecessary sale.

Pond Shopping List

Most desirable koi items

Suitable construction material – liner or blockwork/fibreglass

Efficient filter which is designed to cope with the volume of the pond. Must incorporate a UVc and auto-top up.

A pump that will perform reliably for a minimum of 3 years with limited maintenance.

A range of test kits and measuring equipment (including microscope) to monitor the vital characteristics of the pond environment.

An air pump, capable of pumping to the deepest part of the pond and operating an air dome.

A water purifier to guarantee a reliable source of high quality water.

A quarantine facility for settling in new koi or treating existing koi.

A koi sock, floating basket and bowl for handling koi safely.

An automatic feeder.

A visit to Japan to educate the mind and inspire the soul!

Kill blanketweed and string algae.