Filters

Why do I need a filter?
A pond filter is essential if you intend to keep any concentration of fish in your pond. This is because fish produce wastes such as ammonia which are released in to the pond and will eventually build up to toxic levels unless the water is filtered. This is particularly important when feeding pellets high in protein which result in higher levels of ammonia production.


Which size of filter do I require?
Choosing the correct size of filter for your pond is critical to its success. You must establish the volume of water within your pond and take in to account the amount of direct sunlight your pond receives. For direct sunlight add 20% to 50% to the volume. Due to the higher density stocking and increased feeding associated with Koi carp a much larger filter is required, see our product descriptions for recommended filter capacities.


How do I calculate the volume of my pond?
If your pond is rectangular or square the easiest way is to use our pond volume calculator ( on the left). Simply enter the length and width of your pond as well as the average depth. Enter your dimensions in either feet or metres, the answer will be displayed in both litres and gallons. For circular ponds multiply the radius in metres by the radius in metres and then multipy by 3.14 this gives the surface area. Multiply this figure by the average depth this gives the volume in cubic metres. Multiply this figure by 1000 to get the result in litres.


e.g. For a pond 2.5 metres in diameter and 1.5 metres deep.
(1.25(r) x 1.25(r) x 3.14 = 4.9

4.9 x 1.5(depth) = 7.35

7.35 x 1000 = 7350 litres.

Why do Koi require more filtration than other fish?
Koi are the largest fish usually kept in ponds and can reach 2 - 3 feet (60 - 90cm) in length. As such they consume more feed and produce more waste than other ornamental fish. To cope with this the filter needs to be around twice as large as for other species. The filter and pump need to be capable of filtering the water in the pond every one or two hours. Another reason is that Koi require much higher quality water than other pond species and this is achieved by using a filtration system that ensures no ammonia or nitrite is present in the water.


How does a filter work?
A filter works in two stages, firstly removing solids such as fish waste and silt and secondly by the removal of toxic substances such as ammonia and nitrite. Solids are removed by passing the water through brushes and /or reticulated foam. The trapped solids can then be flushed away via the drain valve (where applicable) or washed out of the foam and brushes. Use only pond or de-chlorinated water to clean the filter as chlorine will sterilise your filter. Once the solids have been removed the water then passes through the biological media which is host to millions of beneficial nitrifying bacteria that convert toxic ammonia firstly to nitrite and secondly to less harmful nitrates. These nitrates are in turn absorbed by plants and also converted into harmless nitrogen gas.


How often should I clean my filter?
This largely depends on how heavily stocked your pond is and the time of year. We would recommend that you check the build up of solids in your filter weekly to begin with, especially during the summer, until you find the frequency of cleaning that suits your pond. The biological components of the filter should only be cleaned once a year unless there is a blockage or solid waste has been allowed to foul the biological medium. These should only be cleaned with pond or de-chlorinated water as the chlorine will destroy the beneficial bacteria.


Will a filter give me clean water?
A correctly sized filter is the only way of ensuring clean water within your pond to allow fish to thrive. When used in conjunction with an Ultra Violet Clarifier not only will the water be clean enough for your fish but it will also be clear. Remember that the correct filter will ensure the water that is cleaned of suspended solids and toxic waste it may still contain living algae which can give green water but are not generally harmful, unless left to get out of control. These algae can be removed by using an Ultra Violet Clarifier.


How long does a filter take to reach full working capacity?
This is dependant on the temperature of the water. In the warmer months it takes 4 to 6 weeks to reach full working capacity and up to 3 months in winter. This is because the beneficial nitrifying bacteria gradually build up a population on the bio-media. During this time the water quality will vary considerably and should be tested regularly. During the maturing period we recommend only stocking a few goldfish in the pond as they are more tolerant of these changes than other fish. To speed up the maturing process you can add a filter primer, basically bacteria in a bottle. If you are already have a working filter you can swap some of the mature media from this (no more than one third) with media from your new filter. This will speed up the maturing process considerably. The maturing process of a new filter is as follows:- Firstly Nitrosomonas bacteria will grow and convert harmful ammonia to Nitrites, when these have reached their maximum population ammonia levels will drop to almost zero and nitrite levels will be very high. Then Nitrobacter bacteria begin to colonise the media and convert the nitrites in to less harmful nitrates. When fully colonised both nitrite and ammonia levels will drop to almost zero. At this point new fish can be added a few at a time to allow the filter to build up the bacteria levels even further.



Ultra Violet Clarifiers

Do I need an Ultra Violet Clarifier (UVC)?
This depends on whether or not you want to have clear water in your pond and the amount of shade and plants your pond has. As far as the fish are concerned they would probably prefer the water to have a slight green colour as it offers some shade and natural food. However it is dangerous to have "pea soup" coloured water as the oxygen levels can drop to very low levels during the hours of darkness. An Ultra Violet Clarifier is therefore recommended if you want crystal clear water, your pond is in full sunlight or you have little or no aquatic vegetation.



Water Test Results

When I test the water what results should I looking for to ensure healthy fish?

When you test your pond water you should mainly be monitoring levels of ammonia, nitrites, nitrates and oxygen. If testing a newly filled pond chlorine values should also be tested and should be below 0.002mg/l. Ammonia levels above 0.01mg/l are to be avoided and the fish are in danger from 0.2mg/l upwards.



Pumps

Why are different pumps recommended for each filter?
We usually recommend two different pumps for use with each filter. The lower rated pump would be used where there is little pipework running from the pump to the filter and there is little difference in height between the pond water level and the filter, this difference is known as head. The higher rated pump is for use where there is a long distance between the pump and filter or a lot of bends in the pipe. The larger pump will also lift the water higher where larger head is required. Remember that every bend and device between the pump and filter as well as the pipe itself will reduce water flow. It is therefore better to go for a larger pump if in doubt, all the pumps we sell are adjustable and can be controlled further with a ball valve if required.



Quarantine

Should I use a quarantine tank?
Yes, a quarantine tank is an invaluable tool for every pond keeper. It should be used to quarantine new stock before introduction to the pond, here the new fish can be closely monitored for any abnormalities and treated accordingly. The quarantine tank is ideal for isolating sick fish from the rest of your stock, this reduces the spread of infection and allows only those in the tank to be treated and monitored. It is also useful to have somewhere to keep your stock while repairs and maintenance are carried out on the pond.


How long do I need to run the quarantine tank before adding fish?
The filter within the quarantine system should be fully mature before fish are added. If you have the space it is ideal to run the system continually with just a couple of goldfish and within 4 - 6 weeks the filter should be mature. This process can be speeded up by using a filter primer. The fastest way to get the system up and running is to use some of the mature bio-media from your pond filter. Carefully remove some media from the filter,(not more than one third), and transfer quickly to the quarantine filter. Ensure that the quarantine system is filled using de-chlorinated water or use a de-chlorinator before adding the media. Replace the media removed from the pond filter with new. The water quality should be monitored very carefully during these times.


How do I keep the quarantine filter active?
If left running the quarantine system should always have a couple of healthy goldfish in it, these should be fed regularly in order to keep the filter active. The ammonia and nitrite levels should be monitored just as regularly as the pond system to ensure perfect water quality, this way the quarantine tank is always ready when needed.


How many fish can I keep in the quarantine tank?
This is largely dependant on how long you intend to keep the fish in the system. For a short quarantine of 24 hours you are only limited by the oxygen in the system and this should be carefully monitored. The addition of an air pump is recommended for particularly heavy short term stocking. For longer quarantine periods it is the production of ammonia and nitrite that determines the maximum stocking and as with the pond system, fish should be added gradually to allow the filter bacteria to increase in number. Careful monitoring of the water quality will indicate whether too many fish have been stocked. As a guide we would recommend a maximum of 200cm of fish within the system.



Pipework

Which type of pipework should I use?
In pump fed systems you should always use the largest diameter pipework possible. The larger the pipe the less friction is generated therefore you lose less flow through the pipe. Remember that every elbow and bend reduces the flow rate so these should be kept to a minimum. It is generally advised to use flexible hose and/or solvent weld pipe from the pump to the filter and push-fit pipework from the filter to the pond.

If you are using a gravity fed system use solvent weld pipework of around 3" from the pond to the filter and solvent weld pipework from the filter pump to the pond.

Remember that solvent weld pipe and fittings use a cement that melts the outer layer of the plastic and when assembled the joint is a permanent weld that is very strong but cannot be undone. This is the pipework to use when the pipe will be buried or inaccessible.

Push-fit pipe and fittings rely on "O" rings to seal the pipe and properly assembled give years of leak free use. It has the advantage of being easily altered to add new equipment.