Activated Carbon Media
Activated carbon filter media aggressively adsorbs organic pollutants from medicines and metabolic wastes, detoxifies harmful gases and removes unwanted colors or odors from your water. Coal based activated carbon is more porous and affects your pH less than coconut based carbon. We recommend medicating sick fishes in a separate quarantine tank, but if you have to use your main tank, remove carbon first and replace afterwards to remove remaining medicines. Carbon removes trace elements needed for plant and invertebrate growth, so make limited use of it in planted and reef aquariums, and always monitor your water conditions.
Presoak carbon for an hour to help avoid oxygen depletion. Carbon will eventually exhaust and produce a yellow color in your aquarium (it won't leach adsorbed chemicals back into your water), at which point you should replace it.