Ok what I mean is this. I am planning to build a big wet/dry filter out of a PVC pipe with a diameter of about 4 inches and a height of about 3-5 feet. Feeding it I'll have a 3500gph pump that will trickle the water down from the top of the pipe(since it has to go up to the pipe it will lose power so the flow should be reduced by about 1500gal). Now my main quetsion is, will the lack of light affect the way or effency of the bacteria that develops on the bio-balls?