Math 101
First u need to find the area of the 6in dia. hole the blowers in .
The formula to find area of a circle = diameter / 2 sqared x pi.
6 in dia. / 2 = 3 x 3 = 9 x 3.14 = 28.26 square inches of exhaust .
your passive intake is 8 x 8 sq. = 64 square in .

To be at all effective you need 3 to 4 times the passive area .
28.26sq. in. x 3 = 84.76
28.26sq. in. x 4 = 113.04

You have 64 sq.in. now w/ the 8 x 8 sq. darkroom vent . I suggest another 1 just like it . = 128 sq. in. of passive area total .

Peace man
Crispi :jointsmile: