1fish2fish, just thought I'd add -
Removing the carbon filter doesn't effect your cycle. But it DOES depend what kind you get. If it's carbon and mechanical filtration, if you have a seperate bio-filter it will be fine. If it is pure carbon (and you have a seperate bio-filter), it will be fine. ... I think the main thing is, if you have a bio-filter / sponge, you can remove carbon cartridges in an out without hurting your cycle. I've been doing that for a while, and my cycle has always been fine.
But I'm stopping carbon, it got annoying. Lol :)