Personally I avoid carbon.
Carbon removes most of the toxins out the water, but these toxins are used in the filtration system in the nitrogen cycle.
So if you use carbon, you then starve the filter and cause a mini cycle.
So once the carbon is full or you remove it your get an ammonia spike and if prolonged can cause problem to the fish.
If you have an established tank and do regular water changes then you should not have any problems doing with out.