Btw, the charcoal, I got it from amazon. I got the 3 bags pack, it's listed under aquarium supply. Before using it, make sure you shake it first outside your house. It has a lot of carbon dust in each bag, you dont want that flying around your grow closet. What I do is, I cycle the bags, like every 6 months or so, I replaced it with a fresh bag. To reactivate the used bag, I let it sit under the sun for a few hrs and it will be ready to go again. Same process to reactivate the foam filter. The other added benefit of using activated carbon, it also somewhat control humidity. Excess moisture in the air is absorb by activated carbon, until humidity equilibrium is reach. If the air is too dry, activated carbon will release the trap moisture back to the environment.