Fog system 2.0

Orchid cool vivariumFinally, I have completed an upgrade to the fog delivery system in the cool vivarium. This new system is delivering the fog horizontally, cascading down about two thirds of the back wall and the right side, enveloping the plants mounted there in a cool mist, and filling the whole vivarium with fog in about 3-4 minutes. I have to turn the fans off while operating the humidifier, otherwise they just smash the fog to bits, but this is not a problem, I just had to dial in the timers properly.

The old system just blew in fog straight into the vivarium via a pipe connected to the humidifier on the right side. Although it would fill the vivarium with fog in a few minutes (with fans off) it has not created the atypical cloud forest “fog cloud” that I wanted to recreate. Until now I have controlled the humidifier with a humidistat, and it has worked fine for just raising the relative humidity in the viv. when needed. And by stabilizing the RH above 80% I have successfully coaxed several stubborn Dracula to bloom… chimaera, deniseana, sodiroi, erythrochaete, barrowii and my fantastic Dracula rezekiana has been blooming non-stop for over a year now. But I have a handful more that has tried to bloom all summer, but the buds abort about half way every time – and it is sooo frustrating!! So, I still think it is humidity related. Raising the RH got me about half way there… so I am hoping that creating a cloud of fog for a couple of hours in the morning and also in the afternoon, coinciding with the daily rain cycle might do the trick. Trying to mimic the actual conditions in-situ.

So, I designed a new fog delivery system, with very simple tools. All I did was to drill a bunch of holes into a PVC pipe, attached it to the fog chimney and attached it horizontally across the back and the right side wall, the wet side of the vivarium, capping the end with a piece of cork. I just attached L-brackets with zipties to the EpiWeb wall and then attached the pipe to that with the use of some more zipties. Zipties… love that stuff, next to duct tape it has to be one of the best inventions ever. The amateur vivarium builders’ best friend.

The old humidifier had just stopped working, but thankfully it was under warranty so they sent me a replacement for free. I actually got a different brand all together since they no longer carry the old model. Just as good, I have actually burned out three units this year alone… no doubt a crappy design. This new humidifier is a “Wilfa HU-6” ultrasonic with an option for either hot or cold steam (I will run it cold of course) with a capacity of up to 300 ml/hour and the water tank holds 6 liters. So 1 liter larger tank than the old one, nice. Let’s hope the darn thing lasts longer than 6 months…

For the first evaluation week I will run the morning rain for a good soaking (one minute each) at 7:00 and 7:30, and keep the fog going 15 minutes on, 15 minutes off for two hours until 9:00. Then I will keep it dry during the day (I might have to add on a fog session here to keep RH up, we’ll see) until 17:00 and 17:30 when I will run the afternoon rain  (one minute each). At 20:00 the fog turns back on and runs for two hours until a quick night shower (30 sec.) at 22.00. After one week I will evaluate how it is working and adjust my timers if needed.

The second video shows the vivarium after the fog has been on for about 3 minutes, and then I turn on the rain system.

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By | 2017-10-13T11:25:46+02:00 August 28th, 2011|Categories: Cool vivarium build, Projects|Tags: , , , , , , |13 Comments

About the Author:

Karma is a digital nomad graphic artist and writer, orchid nerd and long-distance hiker from Gothenburg, Sweden. Former editor-in-chief for the Swedish Orchid Society magazine, published internationally and held lectures on orchid culture.


  1. Steve Peralta August 31, 2011 at 01:06 - Reply

    Great post Karma!! Really enjoyed reading about your fog system!! Have a great day/night.. it’s 4:05PM Pacific Standard Time in California, USA.

  2. Carlos Houcek September 2, 2011 at 21:15 - Reply

    Sweet Karma, just like all of your orchids, YOU are also one of a kind!!!


    • Karma September 7, 2011 at 09:14 - Reply

      Thanks a lot both of you! 🙂

  3. Mad-Milk October 3, 2011 at 08:26 - Reply

    That’s one monster fogger! I found one from… No lucky reptile for me… DIY is the way to go in foggers 🙂
    Have you spotted cheaper models with just the volume of fog like in wilfa, but with less extras? (Like without warm mist, mineral filter or internal humidity check?)

    • Karma October 3, 2011 at 08:35 - Reply

      I did not actually choose this fogger, it was the replacement unit (under warranty) for another model with a lot less bells and whistles… So far it is working fine, but I will most definitely either go DIY or professional for my next unit. These personal units don’t seem to last… I was thinking of just making something simple myself using simple fog discs (like they use in pond installations). they are cheap and you can replace the membrane when it wears out, the first thing that usually goes I have noticed. If you have figured out a good solution already, please do tell. 🙂

  4. atomic October 9, 2011 at 04:25 - Reply

    I have a fogger built from ultrasonic fog discs like you describe. My model has three discs in it, fits into a float that keeps the fogger at the surface of the water, and has a water sensor in it that shuts it off if dry. It produces a wonderfully fine fog, but the fog tends to collect in the bucket and sink to the bottom of my case. My solution was to point a fan directly into the bucket, which blows the fog all over the case. I ran a water line to the bucket and filled it by hand, but kept forgetting. My solution was to add a float valve (like a valve used to fill the water tank in a toilet) and leave the water on – the valve tops up the water level in the bucket as the fogger runs. I control the fan and fogger’s power supply with a humidistat, set for 80%, and the whole thing runs fully automatically – at least until something burns out (which is about once a year). This fogger can fill my 1.3mx1.3mx2m case to 95% RH (from about 30% RH) in 10 minutes, even with an exhaust fan running. I have seen fog disc assemblies that have 5 discs and 10 discs that would go faster still, but this is enough for me.

  5. Karma October 9, 2011 at 12:34 - Reply

    Thanks a lot for writing about your fog installation, I will add that to my “future build notes”. 🙂 I think I will build something very similar to yours next time. It definitely needs to be modular so I can easily replace the pieces that burn out for a lot less money.

  6. Adam December 28, 2011 at 07:32 - Reply

    More than a little bit in love with your setup. Truly superb. I could sit and stare at it all day.

    • Karma December 28, 2011 at 10:18 - Reply

      Thanks Adam! I am quite pleased with my setup as well. Works great!! 🙂

  7. air June 5, 2012 at 06:41 - Reply

    Hello Karma, as mentioned in my previous comment I am working on a fogging system, it will be similar to that described by atomic above. I am getting a 5-disc ultrasonic fogger with floatation buoy, this will sit in a 20l bucket with water (I intend to work out a float system for auto top-up). In the bucket lid I will make two holes; one to connect to ducting / pvc pipe for delivery to the epiphyte wall, on the other hole I will mount a small computer fan. When the fogger comes on so will the fan, which I hop will push the fog through the ducting to the plants. I have the advantage that I can locate all this in the attic space above the plant room. I’ll be sure to let you know how it goes. Cheers, air.

  8. Karma June 5, 2012 at 08:17 - Reply

    Sounds great! I hope you will document your build and share it with us. I would love to see how you put it all together and how it works out for you. 🙂 I am already working on the first replacement of the wilfa (under warranty still)… the next build definitely need to be more industrial and modular. A float system for auto top up is vital on that future build too.

  9. Pros Alen June 7, 2014 at 16:45 - Reply

    Hi Karma,

    Where have you find this fogsystem ( only the machine ?)

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