Why Use Carbon in Aquariums?
Activated carbon is one of the cheapest, most effective and easiest ways of removing organic pollutants, odours and water discolouration from the aquarium. Aquariums laden with a high organic waste can often experience reduced fish growth and are more susceptible to fish disease. By reducing the organic and toxic compounds in the aquarium water, the water quality improves leading to healthier fish.
Carbon removes organic pollutants from the aquarium water by adsorption, which means the organic compounds are removed from the aquarium water by attaching themselves to the outside of the carbon and then held there by electrostatic force. As carbon adsorbs toxic substances from the aquarium it has a limited working life of about 3 to 4 weeks before it will need to be changed. As most carbon is sold by volume, a general guide of 500ml will treat approximately 50 gallons/225 litres.
In some filter systems the carbon is impregnated into a filter sponge for ease of use. This system will still remove toxic compounds from the aquarium and will still need to be changed according to the manufacturer's instructions.
If you are treating your aquarium with medication, all carbon filtration will need to be removed from the filter as it will remove the treatments, making them ineffective. When the course of treatments has been completed, the carbon can be placed back into the filter.