hey cheers for the link rhizome v useful. according to that link a 25 cfm fam would suit but the only 1's i cam find that small are pc cooling fans and i think i'd prefer something with a bit more beef so was thinkin of something along the following lines: a carbon scrubber at least1.5' long mounted on the roof of the grow cab with the 4" pipe connected to a bath room extractor fan which, mounted on the outside of my cab is rated at 90 m3/hr which roughly works out at (ball park figure) 40cfm. i think this should work out sweet.

on another point i'm going dwc and just went down the pet store and got my air pump and am a lil concerned that i aint producing enough bubbles. the pump is rated at 73 gallons/hour (275 l/hr) if any1's had any success with dwc could ya please post and just tell me the rating of ur air pump,cheers

peace out