Errr, maybe a drawing would have helped us to better visualize your prototype...
But generally, in any ducting or piping work, bends and sudden expansions or contractions are avoided as they sap energy from the fluid movers (pumps and fans) that could have otherwise gone into moving the fluid.
I think also that the high-humidity air will adversely affect your fan that is at the end.
But otherwise, it seems to me that your bong is a pretty standard and proven design. TIP: If it's short, then sprinkle more water to compensate. Don't use too powerful a fan otherwise you'll lose a lot of water (drift water- visible as mist). Build somekinda baffle or screen at the exhaust to capture the drift water droplets.