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 are many different ways in which koi ponds can be filtered. There is often a lot of confusion surrounding filtration, and many new koi pond owners get confused and overwhelmed by the different types of filtration available. Filtration is actually very simple but there are different ways in which it can be done. You can have a separate mechanical and biological system, which is best for larger ponds and then for smaller ponds you get mechanical and biological systems in one.

The most common problem in smaller ponds is the misunderstanding that the sponge inside a submersible water pump is good enough to filter their water. This is not true. This sponge is designed to filter out dirt that could damage the impeller inside the pump. If dirt or even stones get inside the pump it can jam the impeller or even break it. When you notice your water pump is pushing out less water, you must remember to switch the pump off and open the front of the pump to get to the sponge and clean it or replace it. This will make sure that you get the correct flow rate from your pump at all times. There are small filters designed for small ponds, which are available at your koi stores.

Filtration consists of two components, the first is mechanical filtration. Mechanical filtration is the removal of solids such as dirt, algae and organic matter. The second component is the biological filtration; this is where the dissolved toxic excretions of koi are filtered out e.g. Ammonia is converted into Nitrite and then into Nitrate inside the bio filter. This is done by a group of bacteria called nitrosomonas bacteria. When buying filtration for your pond, you must have both mechanical as well as biological filtration. If space is a problem around your pond you will need to use a pressure system. You can use an external pump that sucks water from your bottom drains into a settlement chamber into a koi sand filter that will then run into biological bio tubes and an ultra violet sterilizer. The koi sand filter and settlement chamber are your mechanical filtration, where your solid dirt is trapped. This must be maintained and a weekly hand backwash is required on your koi sand filter. The bio tubes will be your biological filtration where your good bacteria will grow and convert your toxic wast

Maintance of your koi pond for mechanical filtration


Koi keeping is a fun hobby, however cleaning out of your mechanical and biological filters is often not done enough or correctly by koi keepers as it is not much fun to do.  Unfortunately it is part of having a koi pond and below I will discuss and give you guidelines on maintaining your mechanical filtration equipment. In part 2 we will discuss the mainenance of the biological filtration. If you build your Koi pond with the correct filtration the maintenance does not take as long as you may think, and once you have a routine in place it will become a quick job to do.

A common problem that does occur with some koi keepers is the misunderstanding that if you buy the correct filtration you will not have to clean any mechanical or biological filters.  Unfortunately this is incorrect but maintaining the filters is much quicker and easier to do.

Settlement chamber or discharge box:

The settlement chamber is designed to collect the solids before they get to the pump and then the biological filtration.  This box gets the dirt first and needs to be cleaned out and flushed went it is dirty.  When buying a settlement chamber make sure it has a outlet on the box that can run into a storm water drain or waste drain.

Filter brushes are good to use in this box, as they are easy to clean and can be shaken vigorously to get the dirt to fall off.  Depending on the amount of Koi fish you have and the fishes size will determine how often you need to clean out the settlement chamber.  Once a week should be sufficient but look at the settlement chamber to see if it needs to be cleaned more often.

Sand filters

Sand filters are best used after a settlement or discharge box to prevent them blocking up too quickly.  If your bottom drain is connected directly to the suction line of the pool pump you will have to back wash the sand filter more often. When buying a sand filter for a koi pond make sure you buy a Koi sand filter and not a swimming pool sand filter.  They are designed for koi ponds and work much more effectively.  You will be very unhappy if you have a normal swimming pool sand filter when doing maintenance.  The biggest difference in maintenance is that the koi sand filter has a clamp and a screw that keeps the lid on, making opening and closing the filter an easy job. The pool sand filter has 8 to 10 screws to hold the lid in place and undoing 8 to 10 screws 2 to 3 times when doing a hand back wash is not the quickest job.  The sand filter should be cleaned once a week and a hand backwash also needs to be done.  If you only place your sand filter onto backwash each week this is not good enough.  Backwashing your swimming pool like this is fine as chemicals are used to kill algae and microorganisms in the water, which therefore take up less space inside the sand filter. Koi ponds don’t use chemicals and the sand that is used in Koi sand filters is 3-5mm which is much larger than what you would use in a swimming pool filter.  The courser gravel is heavier and is not stirred that well by a normal backwash, therefore it is important to open it up and stir it manually by hand before doing a normal backwash. Doing a hand backwash also breaks a crust that tends to form on top of the sand filter.

By doing regular maintenance on your koi pond you will see the benefit in your koi pond and the water clarity will be clean and clear.


Parasites & Infections…. When things go wrong

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Like humans, koi rely on a healthy immune system for protection from disease. Many of my articles focus on those aspects of koi-keeping that are necessary to keep their immune systems healthy, however, every now and then one needs to consider some of the health problems that can arise.

In spring and autumn when temperatures fluctuate widely it is imperative that you pay special attention to your koi. Make sure they are eating their food and swimming actively around the pond, if not you need to seek advice from your koi dealer. Koi are ectothermic, in other words they control their body temperature through their environment and their physiology is thus directly affected by the water temperature. Their immune systems work best between 18 and 28 degrees C and you will find that if your koi do get sick it will usually be during the cooler months.

Koi that are stressed over an extended period are more likely to suffer ill health because, when stressed, they release corticosteroids and catecholamines, hormones that ultimately suppress the immune system. If stress is chronic due to poor water quality their immune systems will be suppressed for longer than is safe and they will be especially vulnerable. Weekly water testing can save the lives of your koi (and reduce your own stress levels, because seeing one’s koi sick and struggling is extremely stressful).

What to look for

These are some of the most common problems that may affect your koi – if you familiarise yourself with the symptoms you will be able to recognise them more easily. If you notice a problem, immediately obtain assistance from a knowledgeable koi-keeper.

White spot

This parasite, Ichthyophthirius multifiliis, is visible to the naked eye as a series of white spots on the koi. The first few spots usually develop on the fins and infected fish will start to rub against objects in the water and may be restless. As the parasite spreads the fish lose their appetite and become lethargic. You need to pick up the infection early and begin treating immediately; if your fish get to the lethargic stage before you notice the problems then your chances of success are lessened and the infected koi may die.

Costia, chilodonella and trichodina

These three forms of parasite are all microscopic, so the first signs that your koi are affected will be a change in their behaviour. The koi scratch themselves as best as they can in an attempt to relieve the discomfort and to rid themselves of the parasites. The koi will scrape their bodies on the sides and bottom of the pond (called ‘flashing’) and they may also swim in a strange way, spiral or jump. The parasites also do further damage to the immune systems of the affected koi, and make them more susceptible to other health problems.

· Costia attaches itself to the gills, skin and fins of the koi. Affected fish become increasingly lethargic and may show signs of oxygen starvation.

· Chilodonella reaches high numbers when water quality is poor and koi that are exposed to bad water conditions become very susceptible to it. Chilodonella feeds off mucus, cell debris and bacteria.

· Trichodina also feeds off mucus, cell debris and bacteria. It attaches itself to the koi using a ring of small barbs.

Gill flukes and other flukes

Flukes are also only visible under a microscope; they look like small worms and attach to the skin and gills by means of hooks in their posterior body region. Flukes may attach themselves to any part of the koi, but gill flukes specifically congregate in groups at the openings of the gills and feed off the tissue, making it increasingly difficult for the koi to process oxygen from the water. Gill flukes also carry bacteria, which enters the gills through the holes drilled by the flukes and causes bacterial gill disease and ulcers.


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Well Known for koi Keeping and have been In Kodama Koi's Magazine hi-lighting our way of raising koi. 

Proud cofounder Off the Tri-State Zna Koi club

Numerous Koi trophies and awards for koi keeping.