growing in a pc is hard. i had two plants in there.
how to make a small(but effective) carbon filter.
1. get a gatorade bottle.
2. cut both ends off so u have a hollow tube
3. get two socks and some duct tape.
4. cut the ends off of the socks so u can spread them over the ends of it(tightly), enough so that both ends will touch each other.
5. get some activated carbon and fill the gatorade bottle then tape on the other half of the sock.
6. put some fans on each side(in and out). there u go u just made a good carbon filter
hope this goes well for u