While many coldwater ponds can potentially thrive without supplementary filtration, when keeping koi carp, installing a suitable pond filter is vital!
Koi ponds are generally very large, and will usual contain several fish; which of course, generate a lot of waste! Ensuring that your pond filter is fit to support the health of your fish is really important, and is one of the core elements that you should consider when building your koi pond.
What does filtration do?
Pond filters serves two purposes: They keep the water clear so that you can actually see your fish, and keep the water clean so that your fish will be healthy and thrive.
There are two main types of filtration: One of these is biological filtration, which minimizes the buildup of potentially harmful toxins within the water by effectively cleaning and recycling biological waste, and the other is mechanical filtration, which manually removes particles and dirt from the water. Most koi pond filters utilize both types of filtration within one unit.
Different types of koi pond filters
There are various different types of pond filter available. The type you choose will depend on the size of your pond, the layout of the build, access to filters for cleaning and maintenance, and personal choice. Here are the main types of koi pond filters that you might wish to consider:
Pump fed systems
Pump fed filter systems work by mechanically pushing the water around the pond and circulating it through the filter, where biological contaminants and large particles of waste are held for later removal, before the clean, filtered water is re-circulated back into the pond.
Gravity fed systems
Gravity fed systems work by siphoning waste and debris from the bottom of the pond, where they tend to build up, through a pipe that connects to the filtration system, cleaning the water before recirculation. The water level within the filter therefore remains level with that of the pond, and provides an effective cleaning and filtration regime. This style of filtration is the type usually recommended for koi ponds.
Bead filters/swimming pool filters
Bubble bead filters are the type of filters most usually used within swimming pools, but are eminently suitable for use in larger koi ponds too.
These filters also often incorporate a UV sterilizer to keep the water clear and prevent algae buildup which can give your pond a green tinge. Today, bubble bead filters are also produced specifically for the pond industry, and should not be too hard to source!
Most koi ponds utilize mechanical filtration as described above, which includes an element of biological filtration too. However, it is possible to install biological filtration only within your koi pond, by building an additional sump or filter box containing various media to clean toxins from the water.
In order to successfully use biological filtration only, however, your pond should be well established, stable, and not be likely to undergo any major changes, such as the addition of more fish. Biological-only filtration also requires very regular monitoring, and may be better left to the experts!