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Cutting Chemicals and Contaminants with Aquarium Charcoal

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Cutting Chemicals and Contaminants with Aquarium Charcoal

When it comes to aquarium filtration systems, there is no shortage available to hobbyists looking to keep their fish’s environment clean and healthy.  Using aquarium charcoal as part of a chemical filtration regime is a viable option due to its ability to break down dissolved organic compounds (DOC’s), odor and color contamination in tank water.

What is Aquarium Charcoal?

Aquarium charcoal (also known as "activated” charcoal or carbon) is a substance popularly used in filtration systems as a means to adsorb chemicals and harmful organic waste in the water.  These chemicals could potentially stress or weaken the fish, while things like phenols lead to unwanted "fishy” odors in aquariums.  Because charcoal is a highly porous substance, it has the capacity to attract and hold these organic chemicals inside of it, such as:
  • tannins (leading to discoloration)
  • phenols (leading to odor)
  • chlorine and chloramine (used to sanitize tap water of bacteria)
  • hydrogen sulphide
  • detergents and contaminants such as bleach or arsenic;
  • small amounts of heavy metals such as mercury, iron or chelated copper, and
  • medications
Because charcoal successfully adsorbs medications, it’s important to note that it should be removed from the filter before treating fish for any sickness or disease.  Once the treatment is completed, the charcoal can be safely reintroduced to the tank.

Forms of Aquarium Charcoal

Often coming in the form of a black sponge or small granules, coal or wood-based charcoals are commonly used in most filtration systems.  The typical form used in aquariums is GAC, or granular activated carbon.  When deliberating brands of charcoal, it’s important to consider weight for the given volume.  Lighter charcoal (though more expensive) tends to yield better results due to its increased porousness and ability to adsorb unwanted chemicals.  Fine particles in the water can clog the tiny pores of the charcoal, but most filters use a fiber pad in the water flow to prevent this from happening.  Additionally, DIY methods, like an old stocking, can serve as a handy solution to keep your filter free from blockage.
Because charcoal binds with the organic compounds it filters from the water, it eventually becomes saturated and loses its capacity to remove these contaminants.  In order to remain effective, it must be regularly changed, with the typical rule-of-thumb being every 2-4 weeks.  However, occasionally rinsing the charcoal can temporarily refresh the batch to extend its lifespan and use.

What it Doesn’t Do

Charcoal will not eliminate ammonia from the water, but instead leave ammonia traces behind in the process of chlorine removal.  This ammonia is highly toxic to fish and enters the aquarium water through a number of ways such as the tap or through the decomposition and breakdown of proteins.  Additionally, aquarium charcoal will not remove nitrites or nitrates, which means that other methods such as water changes must be used when initially setting up your tank.
Proper maintenance of an aquarium is essential to the preservation and longevity of your fish while keeping them healthy and stress-free.  Using aquarium charcoal in a water filter helps keep their environment clean by absorbing harmful organic waste, while also eliminating unsightly colors and undesirable odors from the tank.