recirculating fan questions
I've finished installing the fan box on my plywood paludarium and wanted to get some opinions about the fans. The L-shaped fan box runs along the top of the front and side that have viewing panels. It is 2.5" tall (so sized for 60mm fans) and has openings for 4 fans on the front (60" span) and 2 fans on the side (28" span). The plan is that the fans will draw air from the top of the viv and blow it down the glass viewing panels, providing circulation and hopefully helping to keep the glass clear. I've attached a basic cross section of the box to illustrate the principle.
Anyway, here are my questions. What kind of airflow do you think is appropriate in a circulation system like this? Is there a general air turnover rate rule of thumb analogous to aquarium filtration? The emersed portion of the paludarium will be around 200gals or around 23 cubic feet. Does it seem seasonable to have 6 fans running at 15-20cfm?
Secondly, what kind of noise level do you think is appropriate? Are 32dBA fans an acceptable level of noise?