Fish Pond Filters - An Overview

The fish pond filter is an essential part of the fish pond set-up, as it removes solid waste and ammonia from the water. Without it, there is no efficient and reliable way of maintaining the water quality in your fish pond. It is therefore unkind to keep fish in a fish pond without adequate filtration. It is important, therefore, to have an understanding of how a fish pond filter does its job, and how to look after it. The fish pond filters are designed to remove ammonia, solid waste, as well as odors, colorants and pollutants from the fish pond water.

Solid waste is sieved out of the fish pond water as it passes through the fish pond filter's foam sponges. These can then be easily removed from the fish pond filter and cleaned. In some fish pond filters, advanced carbon impregnated sponges also mean that pollutants, colorants and odors are removed from the fish pond water. Ammonia is produced by the fish and is very toxic to them, with even low levels leading to ill health.

Fish pond filters remove ammonia biologically, utilizing naturally occurring nitrifying bacteria. These bacteria convert ammonia into nitrite, and then they turn nitrite into harmless nitrate. Once the fish pond filter is up and running properly, it will permanently keep ammonia and nitrite levels in your fish pond at virtually zero.

Before the fish pond filter can efficiently remove ammonia and nitrite from the fish pond water, it must first become fully colonized with nitrifying bacteria. This can take some time and is a process known as fish pond filter "maturation". Each time a fish is put in the fish pond it will add to the total amount of ammonia being produced. The ammonia level in the fish pond will therefore increase slightly. Because there is more ammonia for the bacteria to utilize, they start to multiply until there are enough to use all of the ammonia being produced inside the fish pond.

The ammonia level in your fish pond will then fall back to zero. As the ammonia level falls, the amount of nitrite produced by the bacteria in the fish pond filter will start to increase. Therefore, the level of nitrite in the fish pond will rise. The increasing nitrite level means that the bacteria that break it down can start to multiply in the fish pond filter until, as with the ammonia, there are enough to use up all the nitrite that is being produced. The nitrite level within the fish pond can then fall to zero. As this occurs, the nitrate level increases.

In order to avoid dangerous peaks in ammonia and nitrite levels, the fish pond should be stocked slowly, allowing the fish pond filter to "catch up" with each new addition of fish. As a general rule, a few fish should be added to the fish pond every one to two weeks. Once the pond is fully stocked, the ammonia and nitrite levels in the fish pond should remain permanently at zero. It can be very useful to have a couple of test kits during the initial stages of getting the filter going.

Depending on how much waste is being produced in your fish pond, you will from time to time need to clean the media inside your fish pond filter. The fish pond filter foams can be removed and sprayed clean with the hosepipe, taking care not to get any water onto the biological media. This is the media (usually plastic 'rings') that beneficial fish pond filter bacteria live on. The carbon sponge (if your fish pond filter has one) should also be replaced from time to time, as it will become saturated and stop removing pollutants from the water. The biological media should only be cleaned if it needs it (i.e. if it is has solid waste on it), and this should be done in a bucket of fish pond water. Under no circumstances should you clean the biological media of the fish pond filter using water from the hose. The low temperature and chlorine content will kill off the nitrifying bacteria of the fish pond filter, leading to severe fish pond water quality problems.