In aquarium, activated carbon (AC) can be used to remove all the dissolved organic compound (include organic coloring material, organic fertilizer, organic acid...). However, people also think that AC will remove the inorganic compounds, like metal ions, nitrate, phosphate... I think this is wrong since AC cannot remove inorganic compounds as it is an organic material that cannot absorb or adsorb inorganic material.
If people are using DIY fertilizer (direct dissolve metal salt into water), AC will not remove any of it. But if you are using commercial fertilizer, AC will remove some of it since some of the metal ions is organic binded (chelated). The degree of removal for different organic binded metal ions depend on the chelating power of the agent. Since the chelating power of the agent (e.g. EDTA) is different for every kind of metal ions. It depends on the size, charge on the ions itself. If the agent like to bind with Fe2+ first, then all other metal ions will be free in the water.
I think the most disadvantage of using AC in aquarium is that the nitrifying and denitrifying bacteria will undergo starvation. It is because the dissolved organic compounds are the major source of food for them. Also. under this environment, they cannot convert organic nitrogen to ammonia or ammonia to nitrate or nitrogen.
I am just want to share some idea and not to challenge anyone. If someone have new idea or something I am wrong, please have a kind discussion
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