good question... I guess it takes out any impurities I've missed but I have been thinking about this and wondering if I actually need it at all.
When i set up my first little AR380 just over a year ago, I did everything by the book and put in the filter cartridges which are premade with a layer of wool and carbon underneath. I changed them 6-8 weekly. But now I'm thinking I could just go to a wool layer by itself, by it in bulk and save myself a heap of money. The cartridges are convenient, don't leave loose wool fibres to get stuck on the impeller.. but soon start adding up in price.
If I don't really need carbon at all, maybe it's time to ditch it. I'm also running an AR850 now, using the same type of filter system with noodles, black sponge, and wool/carbon cartridge.
ok.. so who uses carbon in their filter and what is the purpose?