Chemical Filters

Chemical filtration works by stripping the toxins right out of the water. This process halts the nitrogen cycle altogether. There are a couple ways to utilize chemical filtration for a pond. Although, this type of filtration costs the most and can be one of the most labor intensive. It is recommended that only small ponds with small fish loads use chemical filtration. If the pond is larger than 1,000 gallons, then biological and mechanical filtration should be used. Here are a couple examples of different chemical filters:


Activated Carbon

A well known chemical filter is activated carbon. Activated carbon is extremely porous and will absorb Ammonia from the water as it passes through it. This is one of the Van der Waals forces, the London dispersion force. Activated carbon looks like a bunch of ruffled up newspapers under a microscope. All of the pores and crevices create an attractive force, which is why Ammonia and other toxins get removed from water. Activated carbon does get full eventually. When it fills up with Ammonia, it needs to be changes immediately. Not only does it stop absorbing Ammonia, but it also starts leeching Ammonia back into the water. Activated carbon cannot be replaced once it is full. It must be thrown away and replaced with new carbon. Do weekly water tests to determine when the activated carbon needs to be changed.


Zeolite is a porous mineral that has the ability to absorb Ammonia. It forms when volcanic rocks and ash react with alkaline water. It can also be synthesized. Zeolite is a cheaper replacement to activated carbon. Unlike activated carbon, which needs to be thrown away once it's full, zeolite can be recharged by placing the stones into a bucket of salt water for about 24 hours. Rinse the zeolite after it comes out of the solution and put the stones back into the pond. The name, zeolite, means "stone that boils". The name comes from a 19th century chemist named Axel Fredrik Cronstedt noticed stones made of this mineral bounce around when they are heated up and boil water.


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