I used to purchase the filters for my top mounted Eclipse filter, and they came with carbon already in it so there was no option. I lived and I learned... I have high phosphates so the carbon was actually increasing the algae in my tank. I used the last Eclipse filter, cut off the floss, removed the carbon and I use the holder empty with phosphate lowering floss. I haven't had a problem with algae or phosphates since. If I feel the water needs a little "polishing" I use little bags of carbon that I bought, I buy Algone, or I use a micro-floss, which is a white colored very fine floss.
No need to carbon! My tank is been better without it, and I am saving a ton of cash on filter media.
Pardon the pun, but I'm hooked!