I have a 180 with 3 HUGE pieces of DW. Couldnt boil them as they were just too friggin huge.
Dropped them in my tank, placed 250ml of purigen in a bag in my 2217 and never saw any staining of the water.
Sure carbon works, but slowly. Buy purigen. Not only does it do the job faster, it can be reused, over and over.
Ehfipimp #273 ( Eheim Classic: 2260, 2217, Eheim Ecco: 2236, 2232 ) Fluval FX5