air exchange in terrarium - Page 2 - Orchid Board

FinnBar · #1 12-21-2007, 03:58 PM

i've understood nighttime humidity is more important while plants open their stomatas at night. during the day they keep them shut as a preventive measure from drying out.

Ross · #2 12-21-2007, 04:06 PM

I run three timers feeding off each other. Here is set-up: appliance timer (simple on-off) set to come on and off at "day length" I choose. Into that timer I have an interval timer plugged that runs the misting system (MistKing). Also the lights and a cooling fan for the lights are plugged into same appliance timer. I have a second timer set to run for 3 hours at night to clear out the tank, so to speak. I feel three hours are plenty to dry things off a bit and I prefer to do it at night because wet nights are bad for plants. Humidity tends to run a bit higher once lights go out, due to lower ambient temps (it's relative humidity, right?) Three hours has provided plenty of drying so far. I still run a fan 24/7 inside the tank to just circulate air (doesn't do anything for air exchange) because it's easier to do it this way. My experience has been that to hold higher humidity for day periods, one needs to NOT do any air exchange (other than passive) during the day. Hope this makes sense. Internal airflow is a MUST if you have no air exchange. Otherwise you will see mold and fungus build up real quickly. As ambient temps of the room the tank is in decrease (like during winter) then it isn't quite as important for air exchange to hold back the mold. That seems to grow best when temps climb in summer (in my experience.) I fought mold all summer using daily sprays of Physan 20 and now I rarely spray, but mold is all gone. Ambient (basement) temps this time of year run approx 18C at night and 22C day. In the tank, I read a bit over 22C at bottom of tank (away from lights) and 24C at top under lights. In summer, figure at least 5 degrees C higher for all readings.

travelfin · #3 12-25-2007, 03:10 PM

HortResearch Publication - The A to Z guide for using CO2. Part 1

Found this sieries of articles on co2. Any comments?

Ocelaris · #4 12-27-2007, 08:58 AM

I have a bit of experience with CO2, but mainly with aquariums with plants. It made a huge difference, but that's in an aquarium when it can be controlled relatively easy. I don't think anyone is truly considering CO2 enrichment, as it's costly to control and in such a small environment as our wardian cases, it wouldn't probably have much benefit. Orchids being relatively slow growers would benefit the least (again it's my assumption), where as tomato crops on a large scale they could justify the costs.

I would agree with the others who said that in order, humidity, air movement, and then exchange are important, the plants unless very densely planted aren't going to run out of CO2 to the point where they are limited in that respect. Just because we're not keeping the enclosure so tightly sealed... Or at least I'm not.

CO2 in an aquarium is easy to control, as dissolved CO2 lowers the pH directly in proportion, so you can use an inexpensive pH meter or simply a metered valve to limit the amount entering at any given time.

However in air, you need a CO2 controller which measures PPM, and is very costly, like in the 400$ range. The bottle and pressure regulator are fairly inexpensive in comparison, costing about 150$ for a 5 lb bottle and single stage regulator (aka beer kegging regulator)... a solenoid based on the day/night cycle might be 20$ or so. The CO2 bottle is only like 15$ to refill, I ended up with a 20lb bottle eventually because they didn't have 5lb bottles one time, and 10lb bottles another... Still was only like 15$ for even the 20lb bottle. CO2 is really really cheap.

I realize that nobody is probably considering CO2 enrichment, but I thought I'd at least expand the scope... Some cautions, saftey is a concern, a bottle of CO2 that escapes rapidly could fill an entire room/house and suffocate everyone. Now that being said, in the aquarium hobby, everyone uses them, well, in reef tanks that is, it's not even a concern for most people.

My setup consists of a humidistat which I picked up on ebay for 25$, which control an ultrasonic mister in a bucket, which blows moisture into the tanks. Basically when it needs humidity it blows into the tank, and when not, it's off. So humidity goes from 60% to 80% roughly. Offsetting that is a vent fan which goes on and off every 5 minutes, so it's a pretty regular exchange, this is throughout the day. During the night All I have is the internal fans moving air, and there are enough holes and crevices that I think it does a decent job of exchange, I was concerned that it was getting too dry at night... The Vandas love this set up, humidity at 60% during the night by the time it gets to be morning... I had a mold problem for a while, but used some physan, and have made sure the internal fans are always on.

FinnBar · #5 12-27-2007, 12:32 PM

i've been using co2 in my freshwater tank back in the day too.
co2 dissolves easily into water but i also did my best to keep it there. it's easy to aerate it out.
i think co2 addition in an orchid tank would need a well sealed tank.

orchids thrive without added co2 whereas some aquarium plants wouldn't. i think because it's way harder to maintain suitable conditions for (certain) aquatic plants in a small enclosure than it is for orchids.
i believe the lack of co2 in an orchid tank most often isn't the limiting factor. when it's not, adding it won't make a difference.
unfortunately i couldn't open the link travelfin posted. i'm hoping i'll have better luck when i get home this weekend.
interesting topic IMO.
oh, and if somebbody wants to give it a try there's the inexpensive DIY yeast bottle thing a lot of people use in fish tanks. i don't know what it would do in an orchidarium..?

travelfin · #6 12-27-2007, 01:31 PM

thanks for your good answers. been doing more research myself google co2 orchids ppm gives some interesting answers. also found out thaat plants use 4gr of co2 per hour per m2 so without any air exchange you use the co2 in a 1m3 in a half an hour. also this is interesting link
orchid food, fertilizer for orchids,non urea fertilizer just as this GeneticArchaeology.com - Professor Probing The Evolution Of Tropical Orchids (7/14/2007)
Interesting which orchids are cam and c3 and the difference in culture.
Bloody internet and all the answers you get depending on your search

FinnBar · #7 12-27-2007, 03:17 PM

Quote:

plants use 4gr of co2 per hour per m2

i suspect m2 here means the surface area of the leaves. there has to be some kind of differentiation between different sized plants in the equation..?