I've used carbon for the last 4 or so gardens that I had. I didn't have any plans to go on, but I used to sell them so I was ok on that one

From my point of view, both my cheapo version, and the one seen at the store's work exact. They do a pretty good job! the store bought claimed about being able to hold .3 microns if I remember right...hehe...gettin old.
The store bought had about 2 gallons of act/char. which had a 350 cu.f inline running it. Clearing a room 11x11x8'. Anything outside the room wasn't infected, but when you walked in the room...diffrent story. Of course you just walked into a garden full of WR!
Again down the road I scaled down and went small...cabinet stuff!
So I started to make my own design that would work well.
Just made a smaller version, using about 3/4 gallon act/char, with a 150blower, clearing an aera of 2'x2'x6'. That works like a champ! Gets in the way alittle but it's worth it!