Introduction

When building a Koi pond, it is vital that you allow enough of your budget to buy the items that are essential for your pond to run well. Some of these items can be classed as essential rather than optional and, of course, the cost of each item will vary depending on the size of your pond.
    An average pond size today would be in the region of 4,000 gallons and this would be a gravity-fed pond. With this in mind, the following costs should be budgeted for (these are approximate):

Essential items

Bottom drain: £19.95
4in slide valve: £45
Medium (30in plus) vortex: £225
Filter system: £600–£1,100
Pump: £260
55W UV unit: £130
 

Recommended

Skimmer: £40
Pump for skimmer: £180
Heater, heat exchanger or heat pump: £330–£2,000
50l air pump with airstone: £130
Water purifier: £100–£300

As shown, the items listed as essential will be required whichever way you build your 4,000-gallon pond – this will result in a functioning pond, but it is worth considering some of the recommended items. With those, some can easily be fitted later, like a heater, but if you think you might install a unit at a later date, make sure that you have a utility supply that will handle the loading, such as gas, oil or electric.

Other items like a skimmer are far easier to fit at the time of construction, because fitting it later will involve draining the pond and carrying out a major job! If you are happy to go for just the essential items, you would be looking at spending in the region of £2,024.95 with pipework.

We can use this to create a rough pricing guide – if you’re just going for the basics, allow in the region of 50p to 75p per gallon to cover the equipment costs. Although, this does not cover the costs of construction, lining material, removal of waste soil, or any other jobs involved in the actual construction of the pond!

Written by Keith Holmes

Photo courtesy of Flow Images
 

Pump-fed or gravity-fed?

Pump-fed filters are perhaps the quickest and easiest form of filtration to install, because they can easily be added to any pond. On a pump-fed system, the pump is simply positioned in the pond, and the water is pumped from here to an above-ground filter system, which must be located so that the return is higher than the pond because the water returns to the pond via gravity.

Although they are easy to install, pump-fed systems do pose problems. With the pump located in the pond, this creates a potential obstacle for your Koi to damage themselves. Plus, with the pump located in the pond, it is pumping dirty water and so may require more frequent cleaning.

Gravity-fed filters need to be considered at the construction stage of your pond because it is very hard to install this style of filter at a later date. Gravity-fed systems work with a drain, commonly a 4in or 110mm version that is installed in the bottom of the pond. This drain connects to the filter system, which is located so that the top of the unit is the same height as the water in the pond, so if the pond is level with the ground, the filter will be sunk in the ground.

After the filter, a pump is installed, which pumps the clean, filtered water back to the pond. Gravity-fed system have many benefits in that they remove all waste from the pond continually, they are generally easy to maintain, and because the pump is only dealing with filtered water, there is little maintenance needed.

The drawback with gravity-fed systems is that there is more work involved in actually installing such a unit, because it must be done at the construction stage. Plus, there will be a slight increase in the amount of construction required and hence a small increase in cost.

Gravity-fed systems have become the primary option for anyone serious about building a Koi pond. It is vital that you make your choice early on, because this will have an effect on construction, plus some of the filters on the market cannot be used with a pump-fed system. So your choice may affect the efficiency of the pond because of the equipment you’ll be able to install.

 

Written by Keith Holmes
 

Filtration

Multichamber filters operate well in both gravity-fed and pump-fed ponds. Although they have a large footprint, they are cheap and durable. It is vital that you choose the right type of filter and filter media for your pond:
• Your filter system must have the ability to settle out solids, enough surface area to house biological filter media and be able to drain away any waste that collects in the unit
• Circular chambers give better settlement and cut down the chance of any dead spots
• All your filter chambers must have a drain so that waste can easily be flushed away
• If possible, the base of your filters should have a central drainage point with the sides sloping towards it to encourage optimum waste removal
• If you are unable to install a vortex then install suitable media in the first chamber to collect solids
• Three filter chambers is a good starting point – the first settles out solids and the next two are for biological filtration
• Pros: maintenance is relatively straightforward – all that is required is regular flushing of the waste valves, or standpipes, located on each chamber. Periodic backwashing of the media chambers can easily be done by opening the waste valve on that chamber and then powering pond water over the media to flush away any debris.

Although many Koi keepers still consider traditional methods of filtration, such as a settlement chamber followed by a multichambered unit, to be the best, there are other options open to you. Some of these can be used instead of these methods while others can be added to an existing system.

Bead filters
• Look like traditional sand filters
• Have a high-pressure blower for cleaning, which makes maintenance very easy compared to a standard sand filter
• Can be considered as either an addition to your pond or a replacement for the biological filtration stages of your existing system
• Contain thousands of beads with very high surface area
• Pros: small footprint and easy maintenance – simply move the multiport valve and it cleans itself in minutes
• Cons: don’t like blanketweed or large solids
 
Towers
• Either a single tower of media (such as a large-diameter pipe filled with a suitable media) or a number of trays housing the media through which water will pass through – the aim is to create a trickle of water over the media
• Are usually installed as the last stage of filtration before the water returns to the pond
• Pros: may reduce blanketweed and algae, can be home made very easily, very low maintenance
• Cons: lots of heat is lost as water trickles through the filter, must be placed above water level

Showers
• Tend to be stainless steel
• Consist of a number of trays which house media. Water showers down at speed to the levels below, which allows for both biological and mechanical filtration to take place
• Are usually installed as the last stage of filtration before the water returns to the pond
• Pros: new models are less obtrusive than the older versions, can be fed directly from a bottom drain with no settlement
• Cons: lots of heat is lost as water trickles through the filter, must be placed above water level

Fluid sand-bed filters
• A fluid sand filter is worth considering as an addition to your existing system.
• Consists of a cylinder which contains a small volume of occolatic sand
• Water is pumped underneath the sand at a controlled rate to ensure that the water doesn’t take the sand with it
• Pros: massive surface area in a very small space, relatively maintenance-free
• Cons: must be placed above water level, the sand would come out of suspension and compact very quickly if the pump stopped, killing much of the good beneficial bacteria
• The correct flow must be maintained at all times throughout the unit otherwise the sand will not be fluid enough, or it may end up in the pond

Sieve filters
• Inside the unit is a stainless-steel sieve, which can filter down to 100–300 microns or more. As water enters the unit it falls over the sieve, and this continual flow of water pushes the waste to the bottom of the stainless-steel sieve.
• Suitable for both pump-fed and gravity-fed ponds as the main means of mechanical filtration.
• A popular alternative to a vortex for waste settlement before the main filter unit.
• Work well with bead filters or other pump-fed filter systems due to the high amount of waste that they remove.
• Waste can be removed from the unit by opening a waste valve and flushing the unit through.
• Pros: very easy to maintain, smaller footprint compared to a similar-sized vortex, most sieve filters allow two bottom drains to be run into one unit
• Cons: too costly to be economical on small ponds

Eazy Pods
• These units combine both mechanical and biological filtration and are an ideal main filter for pump-fed or gravity-fed ponds up to 2,000 gallons, although they can also be used as an addition to your current setup
• Offer both mechanical and biological filtration
• Easy to maintain

Written by Keith Holmes
 

Vortexes

For effective biological filtration to occur, it’s essential that enough solid material is removed from the water before it enters the biological chambers of your filters. It is also important that the level of waste is kept to a minimum because it will limit the effectiveness of your biological filtration and also harbours parasites and bacteria. The alternative to mechanical removal is to use a settlement chamber, usually in the form of a vortex.

What is a vortex?
A vortex is a cylindrical chamber which tapers into a funnel at the bottom. Incoming water spins around the circumference of the circular chamber – the water normally flows to about a third of the way up the unit – just above where it starts to ‘funnel’. Once the water is spinning inside the vortex the flow slows, allowing waste particles to fall out of suspension and collect at the funnel in the bottom of the unit. Waste collects around the central drainage point. The diameter of this drain will depend upon the size of the vortex; a larger unit will require a 2–3in drain whereas a smaller unit will need a 1.5in drain. These waste drains are generally controlled by a slide or ball valve that can simply be opened to allow the waste to discharge. When the water in the vortex leaves the unit via an outlet pipe at the top, it should be relatively waste-free.

Installing a vortex
A vortex is usually used as the first chamber of a filter system and works best in gravity-fed systems – the water flowing into the unit will travel at a relatively slow speed because it should enter the unit via a 4in pipe from the bottom drain. On gravity-fed systems the chambers will need to be installed so that the top of the unit is slightly higher than the water level in your pond (by 1in or so) – if your pond is flush with the ground then the unit will have to be sunk in-ground.
If you want to use a vortex on a pump-fed setup the unit would have to be positioned so that the outlet is higher than the pond, as the water would flow from here into the next chamber which, in turn, would need to have an outlet above water level. The amount of settlement may be reduced as the water will spin faster due to pump pressure. If you decide to install a vortex on a pump-fed system but eventually realise that the amount of settlement is limited, you can always use the chamber for brushes.
• You may need to install multiple vortex chambers if you will be passing more than 2,000–2,200gph via gravity through your system
• If your pond has multiple bottom drains, the best option is to install a vortex and subsequent filtration system on each drain
• When pumping from a vortex to a bead filter, for example, ensure the outlet isn’t too close to the top of the vortex chamber or it will suck in air

What size?
• Go for the largest-diameter unit possible – this will give you the slowest flow of water through the unit and cause maximum waste settlement.
• Opt for a unit which has a large distance in height from the inlet and the outlet. A good distance between these levels will increase settlement by causing the water to spin more before it leaves the chamber.
• If you are limited in space and still wish to install a vortex it is worth considering the size and flow rate of your unit carefully.
• Cons: a correctly sized vortex unit will have a large footprint, especially if your pond is over 4,000 gallons.

 

Written by Keith Holmes
 

Filter media

Nowadays, there is an overwhelming selection of media available for use within your filter, but they all fall into one of three categories.

Mechanical media will physically remove waste and particles from the water. In modern Koi ponds, mechanical media has changed from brushes that were used in the first stages of the filter system for collecting large waste particles, to the use of finer filter flosses in the later stages for collecting fine particles and polishing the water. The exception to this is on a pump-fed pond where dedicated settlement filtration (like a sieve or vortex) may not be used, and brushes would still be the main mechanical filtration.   

Biological media is used to house the maximum amount of beneficial bacteria to process the waste products from the fish. Biological media can come in many guises, from the traditional rock media like spa or laytag (which are now considered out of date by many), to the new lightweight, easy-to-clean, plastic media (which have a massive surface area in comparison to the volume required).

Then you have media like Japanese matting, which has lasted the test of time and is still considered by many to be one of the best biological medias. Of course, the choice of media may not be one that you make, because many of the filter systems that are proving popular have their own media, and can only run with this!

Chemical media are generally only used if a specific problem arises, for example, if a high ammonia reading occurs, zeolite may be used. Zeolite is a rock media that has the natural ability to absorb small amounts of ammonia, for a limited period of time. Other media that could fall into this category include PIP titanium balls, which cause a chemical reaction to occur as water flows over them and they are exposed to a light source. PIP titanium balls could be considered one of the most expensive medias with a small bag costing over £135!

As for the cost of filter media, it is fair to say that the price of media varies so greatly that it is hard to give you a guide. But if you purchase a filter system, nine times out of 10 you will find that it comes with media included within the price.
 

Written by Keith Holmes

Pumps

First things first, calculate what size pump you need. Work out the gallonage of your pond: length (ft) x width (ft) x depth (ft) x 6.23 = total gallonage. Your pump should be capable of pushing half the volume of your pond through the filters once every hour. A 2,000 gallon pond, for example, will need a 1,000gph pump. Check the flow rate specified by your filter before taking the plunge – bead filters and media showers function at a very high flow rate.

It requires more power to push water through narrow pipes, so always opt for the largest diameter pipe that your chosen pump supports. Items like venturi, UV units and heaters will all affect the flow rate too, so you may have to up the pump’s power if you’re planning on running a lot of equipment.

Where you plan on positioning your filters will also determine what size pump you need. It takes more energy to pump water to filters housed 2ft above water level, say, than to filters housed at the water level. The height to which you want to pump water is known as the head, and most pump manufacturers include a handy graph on the packaging that explains how the head influences the flow rate.

Sump pump
Pros:
• Submergible
• Moves large volumes at high pressure
• Delivers good flow at head height
• Cheap purchase price
• Useful for pumping to waste

Cons:
• High-wattage; expensive to run
• Limited 12 to 24-month guarantee

Cost: £60 to £70 for a 1,500gph model

External/submersible pump
Pros:
• Can be used in or out of water
• No need for waterproof housing
• Low wattage in relation to flow rates
• Ideal for typical gravity-fed set-up
• Long guarantee period – up to five years with some models
• Low running costs – will pay for themselves in a year or two

Cons:
• Older models’ strainers get clogged quickly
• Low wattage means limited flow pressure
• Need to up the size if pumping to head height

Cost: £300 to £350 for a good 16,000lph model with five-year warranty

External pump
Pros:
• High-wattage high-pressure models deliver high flow-rates over long distances
• Manufacturers offer a full-service facility

Cons:
• Low-wattage models lose flow if pumping to height or over distance
• Not designed to be exposed to water
• Short guarantee period (usually one year)

Cost: £250 to £350, but you really do get what you pay for

 

Written by Keith Holmes

 
 

UV units

When building a Koi pond there are some things that you must have, like a pump and a filter. On the other hand, there are items which aren’t absolutely necessary but will enhance and improve your Koi pond – such as a UV unit. UV is short for ultraviolet and is used to kill off the algae that makes your pond water green.

Green water is actually good for your Koi because it protects them from overexposure to sunlight and contains high levels of natural nutrients. Despite the benefits of a naturally green pond, most of us keep Koi to enjoy their colours and to watch them come up to feed; these things simply could not be appreciated in a green pond. Along with this is the fact that, unfortunately, Koi do develop illnesses which need to be spotted early – obviously clear water will allow you to do this more easily than if the pond is green. There are two types of UV unit available:

UV clarifiers
• Kill off the algae that causes green water – although they have no effect on reducing blanketweed growth
• A 50W UV unit will cost around £110

UV sterilisers
• Sterilise pond water, and could kill off up to 99.9% of certain viruses, algae, spores and bacteria – although they have no effect on reducing blanketweed growth
• Typically made form stainless steel, which allows the UV light to be reflected inside the unit and improve performance
• Must be matched to the correct flow rate for optimal functioning
• UV sterilisers are larger than UV clarifiers, and considerably more expensive – from £400 upwards
• Replacement bulb costs are also significantly higher than that of a standard, clarifying UV unit

A typical UV unit, be it a clarifier or steriliser, exposes the water that flows into the unit to ultraviolet light. The UV bulb is housed within a quartz tube to protect the bulb and the electrical connections from coming into direct contact with the water, because glass actually blocks some of the UV light from penetrating the water as it flows through the unit, whereas quartz allows for a higher level of penetration.

A UV unit is installed on the pipework so that the water is pumped through it. Some filter systems are even available with an integral UV filter, but these are more commonly fitted to pump-fed ponds.

In most instances, the position of the UV unit is not critical; but you should always fit a unit after any pressurised filtration equipment as the pressurised water may damage the unit.

Before you buy…
• What is the gallonage of your pond?
• How much exposure to direct sunlight does the pond get?
• You will need 10W of UV light per 1,000 gallons of water
• Where will you install the unit (you will need access to mains power)?
• Most units are not waterproof and should not be installed anywhere liable to flood

Maintenance
UV bulbs should be changed at least once a year or every six months, regardless of whether they are still producing light. The best time to change the bulb is March; then it will be functioning at 100% throughout the summer months when green water will be at its worst. UV light can damage your eyes so turn it off at the mains when you’re maintaining the unit.

At the same time as changing the bulb you could also check the quartz sleeve to see if this needs cleaning, especially if you live in a hard-water area as limescale may have built up. You will need to remove the bulb before cleaning it – use a soft cloth and take extra care to avoid any accidental breakages. In the unlikely event that the unit is not working, always check the quartz sleeve first – if this is intact, you may need to replace the starter (if your unit has one) or it may be that a new starter ballast is required. In many cases, it may be a more cost-effective solution to replace the unit.

 

Written by Keith Holmes
 

Calculations

To work out the gallonage of a square or rectangular pond

• In feet and inches: length x width x depth x 6.23 = gallons
For example, a pond that’s 8ft x 8ft x 5ft deep = 8 x 8 x 5 x 6.23 = 1993.6 gallons

• In metres: length x width x depth = the m3 measurement, then x 220 (because there are 220 gallons or 1,000 lpm3)
For example, a pond that is 2.5m long by 2.5m wide x 1.5m deep = 9.375m3, x 220 = 2062.5 gallons

To work out the gallonage of a circular pond
• In feet and inches: radius (half of the diameter) squared (times by itself) x pi (3.14) x depth x 6.23 = gallons
For example, a pond with a diameter of 10ft will have a radius of 5ft, and a depth of 5ft deep would give you 5 x 5 = 25 (radius squared) x 3.14 (pi) = 78.5. 78.5 x 5 (depth) = 392.50, and 392.50 x 6.23 = 2445.27 gallons

• In metres: radius (half of the diameter) squared (times by itself) x pi (3.14) x depth x 220 = gallons
For example, a pond with a diameter of 3m would have a radius of 1.5m, and a depth of 1.5m deep would give you 1.5 x 1.5 (radius squared) x 3.14 (pi) = 7.065. 7.065 x 1.5 (depth) = 10.5975m3, and 10.5975 x 220 = 2331.45 gallons (because each m3 holds 220 gallons or 1000l)

If you want to work out these figures in litres, one gallon is equal to 4.546l. So a pond of 2445.27 gallons holds 11116.197l, and a pond of 2331.45 gallons holds 10598.77l.

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 of equal depth or that are 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.

 

Stocking levels

With the vast improvements in filter media now, the old adage that you must have a filter with a surface area one-third the size of the pond does not add up. Filters like the Nexus and Bead filters allow for a massive volume to be filtered by a unit with a very small footprint. Because of this, it is impossible to put an exact guide on how big a filter and filter area you will need for a given volume of water, so follow the specifications of the unit that you are purchasing.

With this, as long as you have a filter system on your pond that is maintaining good water quality, the stocking level is up to you. However, the higher the stocking level, the slower the rates of growth you can expect, as well as overall development. Plus, you may find that you have to increase the frequency and amount of water changes and filter maintenance that has to be carried out!

As a very basic guide, the following is still considered by many a good guide for working out the stocking level in your Koi pond:

50in of Koi per 1,000 gallons of pond water (in a well-filtered Koi pond)

A factor that is worth considering (which will ultimately affect stocking, especially with more traditional styles of filter) is the retention time of the water flowing through the unit. The ideal flow rate is the whole gallonage of the pond once every two hours, so work this out by halving your pond’s volume, for example, a 1,000-gallon pond divided by two gives a flow rate of 500 gallons per hour.

From this, you may want to work out the retention time of your filter to see if it is in the region of 10 to 15 mins – the time considered to be acceptable for a pond. To do this, you will need the volume of the filter (the amount of water it holds when in operation) and the pumping rate of your pump. Armed with this information, the following formula can be used:

Filter retention time = filter size/pump rate

For example, if you have a 1,000-gallon pond, you want to be pumping the water at 500 gallons per hour, ideally. If your pump rate is 500 gallons an hour and your filter capacity is 100 gallons then 100/500 = 0.2 hours retention time, which is approximately 12 minutes and within the acceptable time bracket.