Ultimately, what is more important; humidity or airflow??

[ColoradoBirddog]

Ah, a light timer! Yep, I've got one of those. Great idea.

[Ray]

Originally Posted by ColoradoBirddog

Did I miss something Ray?

Yeah... "Oh well"... I guess my thought that maybe you don't need an additional fan does not apply.

Another thought: Do you have to completely enclose the top? If there is a small/moderate opening, the tumbling air from your fan might result in enough exchange, while the humidifier can still do its thing.

[ColoradoBirddog]

Yeah, the way I've got it set up, there is about a 4x10" opening, with the intake fan in place. If I remove it, I can pretty much have it as open or closed as I like.

[Ray]

Originally Posted by ColoradoBirddog

Did I miss something Ray?

Yes. What I meant was that it's too bad more air isn't brought in with the fog.

Another thing to consider: Must you keep the entire top closed? As you have a fan operating, the turbulence it creates will create air exchange through any opening in the top, and it may be that your fogger maintains a decent humidity anyway.

[Paul]

Originally Posted by camille1585

The answer will depend on which orchids you have in the terrarium, and generally both air circulation and decent humidity are needed.

Ultimately? Simple answer ... it depends. As Camille has pointed out, the types of orchids chosen will determine what is more important.

Originally Posted by ColoradoBirddog

The orchids I'm growing in it are Catts, LCs, Phals and a Neofinetia.

The Phals, Lcs and Catts can easily handle much lower humidity unless they are some of the more delicate species. I grow all three types without a terr and my winter RH is typically around 15%. They handle it just fine.

In contrast, I have a couple Lepanthes in an enclosed terr with no air circulation and very high humidity and they have been doing fine for several years now.

Originally Posted by ColoradoBirddog

So, if you can picture, I have a small "room" fan inside, at the bottom of the tank, running 24/7. Finally, I've got a brushless computer fan bringing in the fresh air, again for 24/7.

As Ray indicated, no need to bring fresh air into the tank if you simply don't seal it completely Some fresh air exchange will happen by virtue of having a fan in the terr itself.

Originally Posted by camille1585

Why don't you try running the fresh air fan intermittently? You can do some tests to see how long you can run it without losing too much humidity, then have it run for that duration several times per day. You might end up running it 10min at a time, or an hour, depending on how fast the humidity drops.

Another option is to reduce the speed of the fans. As Camille said, most orchids do not need a stiff breeze ... a barely noticeable zephyr will do just fine.

Originally Posted by ColoradoBirddog

Thanks, Camille. I hadn't thought about that. My terrarium was built with a budget in mind, but if I can find some sort of controller, that may work well.

That's where PC fans come into play. My 90gal terr has three PC fans in it. All 3 fans were used -- salvaged from PC's which had bitten the dust. All 3 have been running 24/7 for almost a decade now. Who can ask for more?

To control fan speed, get a variable AC/DC adapter. If you are lucky and vigilant, you might score one at a thrift store like Salvation Army or GoodWill. Simply snip off the end which would be inserted into the device and wire to the fans. Being able to adjust the voltage on the adapter will enable you to adjust the fan speed.

[ColoradoBirddog]

Thanks, Paul. I do normally just grow my phals in my eastern windows, and they've done very good for me. Them going into the terrarium is more just to see how well they like it. We get very dry here, as well.

It's kind of funny. My tank started more as an attempt to get rid of frustration. I have an established b. nodosa, but I've only managed to get it to bloom once. I had it in a southern facing window, but I guess it wasn't getting enough light in there. Then, my wife got me 3 mounted orchids from Andy's. Sadly, I just couldn't keep 2 of them happy enough, and lost them to our high desert air.

So now, I've got a nice sized tank, that just needs a little balance. Which, I think I might have achieved. For the moment, I've pulled the top PC fan, and I'm just running the fan on the inside, with about a 3x10" opening for air exchange. The humidity is now up in the 60s and more, and I don't need to run the fogger all of the time. I'm going to play around with another timer to see how often I need to run it.

Lousy picture, and the hps light didn't help.

[ColoradoBirddog]

Here it is.

[Swimmingorchids]

wow I am surprised the plants can handle a 400w.

I managed to burn mine badly with a much lower powered led.

Anyway looks like problem has been sorted for you, fan intake on timer and circulating fan on 24/7.

I was personally curious about this myself as I am trying to build a fully automated grow box for some vandas. I am not using any fans at all and just relying on the difference in temperature for air exchange so we shall see - I am going for 80% humidity and sacrificing air flow. Could end in disaster - I know the consensus is to have more airflow but humidity could drop to 40% then. We shall see.

Out of curiosity though, your HPS is on a timer surely or do you have that on 24/7 too?

[Ray]

Originally Posted by Swimmingorchids

wow I am surprised the plants can handle a 400w.

I managed to burn mine badly with a much lower powered led.

It's a matter of wattage AND distance from the lamp.

[ColoradoBirddog]

Originally Posted by Swimmingorchids

wow I am surprised the plants can handle a 400w.

I managed to burn mine badly with a much lower powered led.

Anyway looks like problem has been sorted for you, fan intake on timer and circulating fan on 24/7.

I was personally curious about this myself as I am trying to build a fully automated grow box for some vandas. I am not using any fans at all and just relying on the difference in temperature for air exchange so we shall see - I am going for 80% humidity and sacrificing air flow. Could end in disaster - I know the consensus is to have more airflow but humidity could drop to 40% then. We shall see.

Out of curiosity though, your HPS is on a timer surely or do you have that on 24/7 too?

Like Ray said, it's a matter of distance as well. I did a bit of research to determine how much lux the various orchids needed, and placed light and orchids accordingly. Some of them might be on the higher side, but I tried to position carefully.

You will end in disaster if you don't have some sort of airflow, that I do know. Even a little PC fan will greatly help.

Yes, my light is on a timer. At the moment, 14 hours. In the next few weeks, I'll be stepping it down, following the sun.