The centrifugal type copes better with static pressure losses such as those commonly associated with filters and duct work.
Basically, it will better pull air thru a filter and push it out the duct.
http://hydrofarm.com/product.php?itemid=8095
That'll move the air, will make more noise.
Blow hot air out the top, passive vents in bottom allow cool air to replace exhausted air.
Ozone degrades elastomers, accelerates corrosion, and in excess of 5 ppm it's plain unhealthy. See msds linked below. It takes more than 5ppm to fully cope with strong odors.
www.middlesexgases.com/pdf/msds/p6219a.pdf
Downsides to not using pots (filling whole tray): can't rearrange plants to even canopy, need a shopvac or extreme patience to get all those rocks out of the tray. Otherwise its cool...
All I've ever done is toss a pump in there to circulate my res so it's not completely stagnant. I use 200 gallon res, run for complete cycle with only topoffs and addbacks. Yes, no res change. Just start with a lucas fill, addback to maintain ppm should be only bloom (pk).
As far as your...