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Filtration in your fish tank is incredibly important. Without proper filtration, debris and toxins can build up leading to devastating consequences for your fish. The importance of filtration might be clear, but what isn’t, is how often you should change your fish tank filter. The answer depends on which type of filter.
The actual filter itself – which holds the media – won’t need replacing unless it stops working. Mechanical filter media will not need replacing until it starts to fall apart (in fact, replacing it will do more harm than good), however it will need rinsing once every month or so in tank water. Chemical filters will need to be replaced about once per month. Biological filters won’t need replacing until they fall apart, but you will want to rinse them once per month in tank water.
Mechanical filters force the water through media such as a sponge to remove solid debris. This helps to keep your water clear and fish tank clean. The filter itself will not need replacing unless it stops working, and as long as the filter media is not falling apart, it won’t need replacing either.
In fact, there are negative consequences to replacing the media in a mechanical filter. Beneficial bacteria that acts as a biological filter will build up on the media, and replacing the media will completely remove this bacteria from the tank.
Eventually the filter media will start to clog up and you will need to rinse it. You should do this about once per month. It’s a good idea to combine this with a water change so you can use the tank water to rinse the media. This will help to keep as much bacteria as possible on the media. You can also rinse it in conditioned water, but do not rinse in unconditioned tap water.
If the filter media starts to fall apart, it will need replacing. When you start using the new media, leave the old media in the tank for a few weeks to give the new media time to build up bacteria.
Chemical filters are used to remove impurities from the water. Carbon is the most common media used. With chemical filters, the media adsorbs particles and will eventually fill up and become saturated. Chemical Filters will need to be replaced about once per month, or at least once every two months.
Biological filtration occurs all over your fish tank. Beneficial bacteria breaks down ammonia into nitrites, and then nitrites into nitrates which are much less toxic. This bacteria will grow all over your fish tank, especially in the gravel and mechanical filter. You can also purchase biological filters which just act as another place where bacteria can easily grow. You won’t need to change a biological filter until it starts falling apart, but you might want to give it a rinse in tank water every month or so.