Thanks for all the replies! I'm grateful.
First, to answer Joseia: I plan to start with some of the hardier varieties, possibly even just some mini/micro NOIDs from the local shops. I will likely stick to cattleya an phals to start until I can dial in the system and get an idea of which species to group together in that tank.
What I'm now considering is what MiniatureOrchids mentioned, which is that I don't want to affect the humidity levels too much by exchanging air as a means of moving it as well.
It looks like I'll be setting up dual fans: one to move around air within the tank and one to periodically exchange air. The Arduino is setup to turn on a submersible pump connected to four atomizers if the humidity drops below 60%... if I exchange the air too often, the humidity control loop will kick in too often, I fear.
To Paphluvr's comments about strong fans: I do plan to use computer fans, but I will reduce their speed greatly by running them at lower voltages so they aren't "veritable gales", as you say. I'm using an ATX computer power supply to power the devices, sensors, lights, fans, etc.
P.S. I'd gladly share my notes (and photos, once I've posted 5 times!
) on the Arduino setup if there is any interest... it seems the gardening community in general is very much interested in them, but I haven't found many orchid enthusiasts who are into them. For a controlled environment, they seem to be the perfect solution!
jdusablon 
Hybrid Mode
