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Filters - Nexus (EA) Filter Foam Filter media
Good filtration is essential for a healthy pond and a safe environment for your fish. Koi produce waste and excrete ammonia through the gill membranes. It is the job of the filtration system to remove waste which in the wild would be diluted by the large volume of water or washed away by moving water.
Mechanical Filtration.
This is usually an area of foam mats or buffers or brushes which slow down and strain the water removing solids. These need to be cleaned periodically. Always use pond water when cleaning. (the chlorine in tap water will kill the beneficial bacteria).

Biological Filtration.
This relies on specific bacteria to break down toxic waste products to less harmful substances. There are two stages in the breakdown of ammonia, each stage involving different types of bacteria. The first stage is the breakdown of ammonia to nitrite by nitrifying bacteria, most important of which is Nitrosomonas. The second stage is the conversion of nitrite to nitrate by Nitrobacter. Both of these groups of bacteria are aerobic (need oxygen to live). Sediment building up in the filter will deplete the oxygen levels so it is important to keep sediment to a minimum by cleaning the filter out occasionally. This should be done with pond water if possible to prevent filter die-back.

It will take weeks for your biological filter to mature. We strongly recommend the use of Filter Start in a new filter system.

It is also important that you slowly build up your stocking levels of fish in a new system. Start with just a few fish to let the filters get used to coping with fish waste. Continue to monitor the levels of ammonia, nitrite and nitrate regularly. It can take 2-3 months for a filter to completely mature. Carry out water changes regularly and as the system develops you can add more fish. Patience and diligence will be rewarded by a great reduction in the risk of losing your fish!

A complete filter system, such as those stocked at Causeway Koi, are a great way of ensuring that all components are compatible and are the manufacturer’s recommendation for your pond. However you can easily put a system together to specifically match your requirements. Speak to us if you have any questions.

To calculate pond volume, multiply the length x width x depth (Meters). Multiply by 1000 for litres. To convert this to gallons divide by 4.52.
Ultra Violet Filters.
Biological filtration turns ammonia into nitrate which is harmless to fish (unless at extremely high levels) but the disadvantage of this is that algae love nitrate and you get an algal bloom. There are two types of algae problems, green water and blanket weed. Green water is caused by microscopic algae in the water, it is not harmful to koi, actually it is beneficial, the koi eat the algae and it enhances their colour, but you can't see them! Also in summer the algae use oxygen and leave the fish gasping. There are various ways to get rid of the algae and we recommend a suitable ultra violet (UV) filter which kills the algae as it passes through. Algicide chemicals can be used but the problem will just recur.

Blanket weed is filamentous algae and forms long green strands. It is not really a problem, it uses up nitrate and stops green water occurring, but it is unsightly. Our blanket weed controller is effective against this problem, but UV filtration is not as the algae has to pass through the filter to be killed and blanket weed is attached to the pond