Why would you want humidity higher than 60%? I can't imagine anything that needs more to do reasonablly well.

Lucy,
I have orchids, AV, ferns. I have read that they like humidity about 70% or better. Sometimes my humidity even dips into the 45% range which can only be remedied slowly by misting. This misting a few times daily becomes a pain. My Terrarium is new so I am still experimenting. So far all is great. I never water, only mist. The test will be time, and to see if the jewel orchids and AV flower. I hope to have the AV flower all the time.

Ivan

What are you using to measure it, because if its an exo-terra dial deal, those are REALLY REALLY innacurate

Tom
Thanks. I am using both a T-Rex and a Fluker. The Fluker seems more accurate. They both essentially agree. I just cant figure it out. I have a hygrometer sitting directly over one of the holes in the rigid Tropicaire tube in the terrarium and it barely reads 70%. The company said that it should read atleast 85%. Their customer service couldnt figure out the problem either. I do have a fan in the terrarium bit I dont think that it makes too much difference.

Ivan

If you never water, how do you fertilize? I'm getting a mister for my enclosure and have orchids inside, along with other things, so I'm curious.

Lucy
Why would I want to fertilize a small terrarium? Atleast for a year or two? There should be enough "soil" around the roots from the original planting to provide organics for quite a while.

Going off the description of the tropicaire (I have never used one) it uses an air pump to humidiy the air. Unless you have that pump in the terrarium, you are pumping in the hot dry AZ air. Maybe the tropicaire just can't humidify air that is that dry. Sometimes a dish of water can raise it up a fair bit, especially if it is heated by lights or heat pads. Maybe try something that doesnt pump in so much fresh air.

-DH

Deadhamster,
I agree with your thinking. I did contact Tropicaire. Their engineer spoke with me who is very knowledgeable. He said there still should be no problem pumping in dry AZ air and maintained that the exiting humidity should still be 85% or better. I think I will add the dish of water again and try. I am now misting about 1 pint of r/0 water daily and it is all gone by 12 hours without any in the bottom of the tank. I may try a larger airstone in the Tropicaire. In the meanwhile the plants look great.
Ivan

if you ever get tired of hand misting and you want to raise humidity you could get a misting sytem. I think theyre's a raging debate in another post..........

You could try using an ultrasonic humidifier. Start with a cool mist humidifier and then use appropriately-sized pvc pipes to run from the outlet of the humidifier into a suitably-sized hole in the top of your terrarium. You can tailor the humidity by hooking up the humidifier to a digital timer which will allow you to control how long and thusly how great of an effect you'll have on the relative humidity in your enclosure. Use only a cool mist humidifier though because the warm mist ones are far more prone to bacterial build up inside. Also, distilled water works best with humidifiers as regular tap water tends to have too many minerals in it which will eventually encrust the transducer preventing it from working any more.

Can someone please explain why it's unnecessary to fertilize terrarium plants? Orchids need tons of fertilizer.

Thats the first I've heard of it Lucy, I fertilize mine. My nepenthes get superthrive the first saturday of each month, and a bit of epiphytes delight the rest of the saturdays. And they are certainly not complaining.

-DH

Matt,
I am sure a cool ultrasonic humidifier will work but I just wanted to avoid a big pipe, etc. just for a 20gal tank. It is in the living room and I dont want it to look industrial.

Deadhamster,
I have read many places about not fertilizing a terrarium because mainly the salts will build up, even if you are using a well chelated solution. Also the plants may start growing too fast for the terrarium. If my AV dont flower and my leaves look in need of fertilizer, then I may do it but I bet I will go a year??

Incidently I taped the perimeter of the terrarium top and the humidity is staying at 65-70% so maybe the problem with the Tropicaire is that the tank is not sealed enough. The heat rose to 87 deg so I raised the lighting fixture 2" above the glass lid. Will see what happens.
Ivan

I meant to ask. In regards to your fan, is it on constantly? Becuase no matter how slow it is, if its on all the time then it will murder your humidity. Use a timer so it goes on now and then.

Tom
Yes the fan is on constantly but now that the tank is well sealed, the humidity has stayed at almost 70% for 36hours since the last misting. When I shut the fan off a few hours, it did not change anything. I think only if the top is open a bit will the fan blow out the humid air. Now it stirs up the air but the air has no where to get out. WE shall see. I will take your suggestion if the humidity starts to drop.

Ivan

Update from Ivan
It is about 2 1/2 days since any misting and my humidity is staying 65-70% since I sealed the terrarium top with masking tape. The inside fan is running constantly and not affecting the humidity. Temp ranges from 75-85 degrees since I raised the lights 2" off the tank. Now that I have reached a somewhat workable equilibrium, I will mist every 3 days and place weather stripping on the top edge of the tank instead of masking tape so I can freely take the top on and off.

I guess the bottom line will be to see if my AV flower under these conditions?

All of you, thanks for your help and suggestions.
Ivan

Be careful with a sealed terrarium. fungus and MOLD are your enemies here. you need some fresh air to provide gas exchange. i have a 15 gal (same dimensions)with no fan and a 2" gap in the back and humidity is always 70-90% and thats with pc lighting and hot texas air. temps are 85 day 65 night. you should check out lowes for a good humidity gauge. dont see how you could have that low humidity. i got one that has thermometer,hygrometer, and clock and its digital-very accurate. theyre like $20 but worth it.

I havent had problems with mold. The fan works well and dries everything out pretty quickly and gets rid of condensation. I have a feeling lots depends upon the substrate. If it is porous and holds lots of water, the humidity stays higher. My substrate drains really well and doesnt stay wet, only lightly moist. It seems perfect for terrarium plants but I dont think it is helping me with moisture.

Incidently, what are "pc" lights? Compact flourescents?
I will check out lowes.

Thanks,
Ivan

I do not know the name if the thing, but there is something that you can put in the water, like if you have a small pond or dish of water in your terrarium, that spins around and sends up a mist. It looks like a low fog in your tank. I saw one at Petsmart and it is expensive, like $40.00. It is for terrariums with lizards or frogs that need a very high humidity, tropical environment to help keep their hides moist and not dry out.

Thats an ultrasonic humidifier. They are about $40, extremely unreliable, and have to be replaced constantly. I would avoid it unless there is just no alternative.

-DH

I agree deadhamster on the "fogger." I still cant understand why my Tropicaire doest keep the humidity higher than 70% but I guess that is ok. The only problem is that to keep that humidity I have to keep the tank sealed. I have an inside fan so I have no mold problems but I do have a temperature problem. The temperature averages 85. I think the only solution is to keep the lid open a bit to lower the temperature and settle for a 60% humidity with frequent misting. When the humidity does rist to 80% I do see a growth spirt in the plants.

Ivan