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The use of carbon in the aquarium system
Activated carbon is used quite commonly as part of the filtration system in aquaria. There are many myths and misunderstandings about its use of what it can or cannot do. Some of these myths have been repeated so often it has caused many to believe them to be absolute truths!
Carbon is considered chemical filtration. The effectiveness of activated carbon is based on a three-step process:
First is absorption. Static forces will attract particles absorbing them onto the surface of the carbon. Bacteria that settle on the carbon surface will further consume the waste.
The second process is the diffusion of gases. Absorbed into the carbon the gases are detoxified (i.e. Ozone O3 into oxygen O2)
The third process is called chemo sorption, where particles are irreversibly bound to the carbon.
Carbon will remove a range of substances from water, including:
Organic pollutants, some of which discolour the water with a yellowish tint
Dissolved organic molecules - this is the primary reason to use carbon in most aquaria.
Medications, antibiotics and dyes - this can be useful for removing excess/residual medication, but also means that carbon should be removed when using medications, to avoid removal of the medication during the treatment phase.
Chlorine and chloramines
Fertilizers containing minerals in cheleated form. These cheleates will be absorbed by the carbon as organics.
Certain heavy metals - the amounts will depend on factors such as the solubility of the metal at the pH of the specific aquarium.
Removed organic particles and substances absorbed by the carbon will remain biologically active. Trapped waste particles will still decay and remain part of the aquatic system. Once the Carbon is saturated it “can” release “some” of the absorbed substances back into the water. This is why it is best used on a short-term basis and/or replaced regularly. Indeed carbon is quickly used up and can be removed after just 24-48 hours.
It is important to note that there are certain substances that carbon will NOT absorb any significant amount of, which include:
Ammonia, nitrite and nitrate
Phosphate
Inorganic salts (like sodium chloride)
Trace elements, making it safe to use in reef systems. The uptake of substances like iron, manganese, molybdenum, cadmium, zinc, and carbon dioxide are extremely limited and is insignificant if used only occasionally.
The quantity of carbon needed for an aquarium is approximately 1 teaspoon of carbon for each 30 litres of water.
I think this information will help you.
Keith