Thursday, January 24, 2013

Terrarium ventilation

Supplies needed to set up computer fan for terrarium

     When I left town for the holidays last month, I filled the bottom of my terrarium tank with water to help raise humidity while I was away.  It helped.  Some of the water evaporated, and my orchids tolerated my absense quite well.

     But some of the water remained, and I only got around to cleaning it up today.  While I procrastinated, that standing water had turned into a viscous, moldy, algal scum, which gave off a rather nauseating fruity odor.  As I was cleaning up this mess and wiping the tank with a generous serving of Physan, I decided it was time to install some proper ventilation.

     Every orchid terrarium advice article/thread I've seen strongly recommends having a ventilation system.  Most people suggest using a computer fan as a compact and energy-efficient option.  I actually ordered such a computer fan back in November, but put off setting it up until now because I was hesitant about having to splice wires. 

     Turns out, it was much simpler than I had feared.  There are dozens of articles online describing how to connect a computer fan to a USB cord.  The one I found most helpful, was this youtube video, which clearly showed everything in under 2.5 minutes.

matching red and black wires from computer fan and USB charger

     I sacrificed a USB charger from an old phone that no longer worked.  The only other tools I needed were some wire cutters, scissors, and duct tape.  I cut the fan's wire at the end of the red and black wiring, and I cut the USB cord right before it got to the end that plugs into a cellphone.  When I peeled back all the layers of insulation around the USB cord, there were 4 wires inside (black, red, white, green).  I cut back everything except the red and black wires.

red to red, black to black, and all taped closed

     At this point, all I had to do was peel back the plastic insulation around the black and red wires (this was actually the hardest part).  I curled the metal parts from the two red wires together, and taped everything closed with duct tape.  Then I did the same thing for the black wires.

computer fan ventilation for terrarium

     I've got the fan hanging from the top corner of the tank, where it can blow air diagonally across the entire length of the terrarium.  The fan is fairly weak, but I can definitely feel a breeze from a couple feet away.


  1. Hi Maria,

    I have been meaning to write to you for a bit, as an orchid grower from NYC as well! I have been peeking at your blog for a few weeks now. I actually just finagled my 6" clip-on fan onto my set-up tonight, so strange! It just arrived in the post this afternoon. As a tip, with any sort of humidity trays or standing water that is meant to evaporate, I add a bit of Physan 20 to the standing water to prevent such growth between cleanings. Keep the water fresh and clear for a while longer. Stay warm!!

    All the Best,

    1. Hi Colleen--thanks for stopping by ;-) For future reference, adding Physan sounds like a great idea. Do you keep some standing water in the bottom of your tank normally? Or is mostly just drip water from watering?

    2. Hi Maria, I just have an open set-up. A table in my living room covered with humidity trays in front of a south-facing window. I supplement with a humidifier and a good morning misting - and try to keep the watering in the bathroom.

      Have had luck with adding Physan to the water though. Think I may have read about it on an orchid board somewhere? Add a little less than a tbsp to each gallon of water. The trays have been out for about 3 weeks now and no need to clean quite yet. Truly surprised.

      Congrats on the new fan too! Have heard those DIY-wired computer fans are the best.

  2. Wow, you are such a handy-lady. I ended up buying external fan with usb connector in place and will be installing it this weekend. So, top corner is the place then. I wish they would sell Physan in Canada.