new terrarium needs help

[professor plant]

I have recently bought a 18x18x24" terrarium and filled it with 24 orchids, of inter. temp needs. I need to create a diurnal range that will assist this need. I have a humidifier and two computer fans to help increase humidity and air flow, but my temps stay at 70 F, even with my true 65 watt cool temp CFL running, separated with plexi glass. I have looked at thermal heat pads, but am concerned that they won't properly effect the air temp. I also was told that the bulb may be effected by the humidifier, running past 80% sometimes, so I opted for the plexi glass which also separates the potential heat.

Any suggestions??? I could use the advice. This is my first terrarium and I can use your wise experience.

[ezil]

I'm not sure I can help you, but I'll try. I have 2 terrariums the same size. My indoor humidity is 30% at the best of times, so that's a big issue. I do not know anything about your growing conditions, so what I describe may not be suitable for you. I have removed the mesh screen from the top, and have the lights directly over the plants. For the remaining gap I had a piece of clear glass cut to size. There is still some air coming in through the gaps, and the heat does warm the air a few degrees. For ventilation I have a small computer fan placed a few inches above a container of water. That helps quite a bit with the humidity. I have covered the "floor" of the terrarium with lava rock, a layer of sphagnum moss and have baby's breath and other mosses growing there. The set up works quite well, day time temps vary from 24-30C depending on room temps, and night time from 16-22C. I switch everything off at night time, and open the top or doors a bit. Maybe that's not needed, but I'm a sucker for fresh air.
Oh, I'm sorry: this should have been at the top of the post WELCOME TO THE ORCHID BOARD

[Zoi2]

I can't help with the terrarium but I want to say hello and welcome to the OB!
Joann

[Paul Mc]

Welcome aboard!

I have a question. I have the exact same dimensions and very similar set-up/build as you described. I placed a digital thermometer inside that records the highest temp and lowest until I reset it. I reset it daily and generally I have a the between 10 to 15 degree difference in temperature from the day to night. How are you monitoring your temperatures? Are you sure that you are not already getting the difference?

Be careful with heating pads/cooling pads though. If you have water in the bottom of your terrarium then the cold and heat pads could potentially bust the bottom of the terrarium. I have water in the base of mine for a water feature so I opted not to use them as I could see the temperature change daily already.