If you poke a hole in the bottom of a cup and then put the top side into the water and then press the cup down fast to create a blow hole of air through the hole in the cup you can smell your water way better. This can make you decide if you want to use carbon because it also improves smell of the water.

I did that today with a container I was using as a refuge or quarantine. I was like man the water does smell. haha.

yeah... it also removes the wierd color water from terra cotta pots...

I agree, charcoal is fine. Charcoal tends to make the water crystal clear.

Only bad thing about charcoal, is if you medicate the tank, the charcoal needs to be taken out beforehand or else the carbon will minimize the effect of the medicine. Once the medication does its job, then the charcoal can be put back in.

It is also good to change charcoal every month or so for it loses much of its effect.

But there are more advantages to charcoal than not having any:

crystal clear water
helps with water pollution
helps with an ammonia spike
removes harmful chemicals

it's a debatable topic; I lean more toward using it. Others may not, depends on the needs of the tank or the perspective of the hobbyist.