[edmund83]

for me i will go for option 2.. why? let me explain why i am not choose for others

1) limit space and you will need to control the temperature that suit for plant. personally never test how humidity in the fridge. Properly we need aware on this as well. Do remember fridge only can in stand position instead of sleep position . so mean you are not allow putting lot nep inside.

3) The cost is high and time consume as well.

i will go for 2 which drill a hole and joint with the pipe that you mentioned. But you need to make sure that is not cool air can be leaking out. The problem on this setup i think is the cool air keep on blow to the terrarium. This method might give you a problem on electric consume and $$$$.

As you know the cooler generator will stop once you able maintain certain Celsius. So how to make the cooler generator running in neccesary time? You can thinking a way something like setting a auto timer to control it . Plus, a small fan will help when blow the cool air into the tank.

Do share your project .. cant wait to see the result ^^