Danny-O said:Just take it out. No need to be gradual, like a temp change or altering water parameters. There's nothing about the charcoal that can affect the fish dramatically with its sudden removal.
But do leave everything else intact (the other filter components, gravel, decorations, etc.,) for a few days. I say it this way because the charcoal may support some of your nitrifying bacteria, and removing this while doing lots of other major cleaning at the same time may foment a mini-cycle.
Jericho said:All you have to do is cut the blue filter at the top and pour out the charcoal. Then you will have a mechanical filter that will last you for months.