Homemade activated carbon filter.

Hey growers. I've done a good amount of research on indoor growing from internet to books. My main issue with my setup is my activated carbon filter. Now I planned on doing a closet grow but I said fuck it and decided to get a 3x3 DS90 tent. I bought a 4 in. In line duct fan months before the tent. Along with the 4 in In-line, I bought 4 in. ducting and decided to make my own activated carbon filter. When I did the setup for the exhaust, I noticed that the air flow seemed to be blowing the opposite way, so I thought I installed it incorrectly. But when I disconnected the fan from the ducting, the air flow was fine. So I'm guessing it's the homemade carbon filter I made is messing up the air flow. Instead of using an activated carbon filter (which I couldn't find in stores), I used activated carbon pellets (used for fish tanks) and wrapped an air filter around the mesh wire. I'm considering buying an activated carbon filter on eBay for $46.95. But my initial plan for this grow was low budget. At the end of the day I'm not trying to spend $50. I'm trying to find a way to customize my homemade filter so that it works with the equipment I have already. I need advice on building a homemade activated carbon filter using activated carbon pellets.

From what i have read, the small 4" inline duct fans just dont have enough power to suck the air through a decent filter. I would look into a higher CFM blower thats designed to work with a filter, you loose alot of CFM when you put the filter on due to the back pressure.

This is what I built using them, used Scott Brite cloth to make a bag.

https://www.rollitup.org/t/ultimate-diy-carbon-filter.649682/