[acidrain]

Air agitation makes WAY more fumes than mechanical agitation. I use air agitation, and even in my well ventilated garage, the small exhaust hood wasn't enough. I ended up making a huge exhaust hood from a forced air heater fan.
Consider using a really big circulating pump, or even a simple propeller-on-a-stick run by an electric motor.
As for the cathode, go big.