Fan & Air Circulation
 

Hi, first post.

I've been a longtime orchid fan and grown many, but due to moving and various indoor climates and conditions, been forced to give away or lose them.

Now things are different. I've acquired a 40Gal tank and have programmed an Arduino to control humidity, light and air circulation.

What I can't seem to find reliable information on is how often I should be exchanging/circulating the air... Any thoughts on this?

Thanks in advance.

I grow all of my orchids in terrariums. I have computer fans mounted inside each one and they run 24 hours a day. My terrariums are not completely sealed, they have small vents for fresh air to get pulled inside by the fans. So I have constant air circulation and air exchange. Even with the constant air exchange, I can still maintain humidity levels around 70-75%. Orchids like to get as much clean, fresh air as you can give them.

I grow Latouria Dendrobiums, phals and vandaceous in my terrariums. You didn't mention what kind of orchids you plan to grow, but lots of fresh air and movement is what orchids get in the wild.

Like Joseia, I have a fan running 24/7. I have an indoor 'Greenhouse", a plastic tent with two shelves inside. I have trays of water in the bottom and a fan that is sold as "personal sized" set up above the water. I too have some openings, so there is air exchange. My tent is about 3' x 3' x 1.5', and the fan is about 8 inches across. My humidity ranges from 60 to 80 % depending on how much sun is coming in the south facing window at the moment.

Joseia/Fishmom, just for clarity, are these fans inside the terrarium to move air around within the tank, or are they in the lid and actively drawing air in or out of the tank?

Just trying to understand whether you actively pull/push air into the terrarium via a fan, or if you're just letting a little natural air-exchange with the outside world happen as a result of the combination of small air vents and the fan moving air around within the terrarium.

I've got two fans, one internal for air circulation within the terrarium, and one fitted as part of the lid which draws air out of the tank, but if I have the latter one running 24/7 the humidity drops drastically.

A 40g tank is approx. 5.75ft³ or 5.5ft³ depending on whether it is the long or high version. A small (4") low speed muffin fan can move in excess of 20cfm with high speed units moving 4x that. I would think that would be a veritable gale in that size tank.

Thanks for all the replies! I'm grateful.

First, to answer Joseia: I plan to start with some of the hardier varieties, possibly even just some mini/micro NOIDs from the local shops. I will likely stick to cattleya an phals to start until I can dial in the system and get an idea of which species to group together in that tank.

What I'm now considering is what MiniatureOrchids mentioned, which is that I don't want to affect the humidity levels too much by exchanging air as a means of moving it as well.

It looks like I'll be setting up dual fans: one to move around air within the tank and one to periodically exchange air. The Arduino is setup to turn on a submersible pump connected to four atomizers if the humidity drops below 60%... if I exchange the air too often, the humidity control loop will kick in too often, I fear.

To Paphluvr's comments about strong fans: I do plan to use computer fans, but I will reduce their speed greatly by running them at lower voltages so they aren't "veritable gales", as you say. I'm using an ATX computer power supply to power the devices, sensors, lights, fans, etc.

P.S. I'd gladly share my notes (and photos, once I've posted 5 times! :)) on the Arduino setup if there is any interest... it seems the gardening community in general is very much interested in them, but I haven't found many orchid enthusiasts who are into them. For a controlled environment, they seem to be the perfect solution!

The AC Infinity fans (on Amazon) are excellent for this, and powered by USB too - which means from an Arduino perspective they'd fit in nicely. :)

I've got ventilation holes about one fourth of the way up from the bottom of the tank, and a couple of small vents at the top. The fans are inside the tank behind the bottom vent holes, so they help draw in fresh air. The warm air rises out of vents at the top. The fans are standard pc fans, don't remember the CFM, but they move enough air to gently move the leaves of the orchids. I keep water in the bottom of the tank to maintain humidity and it usually stays between 70-75% relative humidity. The vents near the bottom are not big, just a horizontal series of holes. I use Exo Terra terrariums, you can see the vents at their website, Exo Terra : Natural Terrarium Large / Advanced Reptile Habitat

Also, forgot to mention that I replaced the screen mesh at the top of the tank with a piece of glass. I kept the vents on top for wires and mister hoses uncovered to allow air to rise up and out of the tank.

---------- Post added at 07:31 PM ---------- Previous post was at 07:09 PM ----------

Cattleyas will need brighter light than phals, but if you can put the cattleyas closer to the light and the phals farther from the light, it can work.

As with everything related to orchids, you have to experiment and see what works for you. I have been growing orchids for about 4.5 years, so I am definitely not an expert. I killed quite a few orchids while learning what worked for me.

I would love to read about your setup and see pictures. I think you are on the right track using a combination of fans and misters to keep the desired humidity. I just looked up the arduino site and it probably is a bit too much for me to handle, but this old dog likes trying to learn new tricks. :)