Vivarium w/ orchids
 

I'm planning to set up a vivarium and also planning to plant Orchids. Are tree fern panels good for orchids? Some people use coco panels to plant their orchids in. Will a computer fan do the job for ventilation? I'm also planning to custom build the vivarium w/ vents on the lower front pane. I will be installing misters also from MISTKING.

I'm not an expert on terrariums, but tree fern panels would work out fine for orchids.

I was able to keep my orchids in my 55 gallon tank well ventilated with just a computer fan. I've never used coco panals or tree fern panels, I just grow them on sticks.

humidity
 

Do you keep the fan on 24/7? Does the fan lower the humidity in the vivarium?

Yes the fan will dry things out. Two things to keep in mind

place one fan near the front glass and have it push the air, then place another fan somewhere else and have it suck air. Have both of them controlled via a potentiometer. If you run the fans at full blast, it will be no good. You want just enough circulation to keep the fog off the viewing glass. You can keep it 24/7. My fans go out with the light

I can only keep humidity at around 80%. I dont run the fan 24/7, at least not in this tank. I have it run about an hour after each misting, especially at night so the leaves of the plants get to dry out. But then I also have the mister come on more often at night then during the day. But everything gets dry enough so no fungus problems. I hope.

potentiometer
 

A Fan conroller can adjust the speed of the fan. Is a potentiometer like a fan controller?

exactly what it is. You can get fans with controllers already built in. Look in the case mod websites.

WARNING--Tree fern and orchids
 

Greetings all: Not to be pedantic, but there is a caveat about tree fern. As I understand it, while it is fine for most orchids, it is unsuitable for angraecoids (Angreaecum, Aerangis;). They will die (I'm not sure that we know the specific reason). If you plan to grow angraecoids, use cork bark or a coir fibre mat. If not, tree fern is fine.

This thing thinks a semi-colon is an emoticon? Sheesh...