Hi there! =) I dont think that most people on this site have the "classic" sealed terrarium, most if not all of them have a terrarium that draws air, via fans, into the set up, mine uses fans to bring air into the canopy to cool the lights, then uses a fan to draw a small amount of air into the set up from the canopy via two one inch holes drilled into the plexi cover, that fan circulates warm air from the canopy lights inside the set up, I made it this way to keep the temp and humidity at the right levels, to much room temp air and the temp and humidity rises or falls to much, (depending on the season, winter, summer) once you get the bugs out of the system it works great! as for "carbon dioxide giving off oxygen" and "how does this work as a cycle in a terrarium which is airtight?" well I dont think that any one has been able to come up with a system of sealed animals and plants that has been proven to work? are you old enough to remember the big "Bio Dome" project? that was one of the biggest projects (sealed vivarium/terrarium) ever! had all the high tech gizmos and gagets and it flopped big time! So there may be the answer to your question =)

Thanks for your reply. Do you think a terrarium planted in a sealed jar would not survive then?

I have dart frog terrariums that are completely sealed. The only fresh air they get is when I open the top to feed. However, that sort of environment is not good for most plants, so I don't see why someone would do that to plants, I use a screen lid if I'm not keeping frogs. Unless you are keeping ghost orchids, those need a completely seaked tank, but other plants would mold and not do so well I'm thinking. But if you still wanted to do it, at least open it once a day or every other day for air flow.

Im dont think it would survive for very long sealed, as back2eight mentioned, "I have dart frog terrariums that are completely sealed. The only fresh air they get is when I open the top to feed. However, that sort of environment is not good for most plants" so even though the tanks are sealed, they do get fresh air, almost daily if Im not mistaken, when the frogs are fed, and did mention that the sealed terrarium is, "not good for most plants" give it a try and let us know how it goes =)

Plant terrariums can work if sealed, but not ones with animals in them.

I'm confused...I thought terrariums were supposed to be air tight. I had mine this way, but after reading the above, I have the top slightly open to allow air in. Is this correct? Won't this prevent moisture from condensing on tank and moistening the soil? Although I still have some moisture on the tank walls, even with the top ajar. This is only my second attempt at a terrarium, so I'm a newbie..any advice appreciated. I have a very basic setup with a small pothos, 2 small ivy's, a baby's tears, and 2 polka dot plants (that will have to be pruned often, I know)in a 15 gal tank. Very simple, I hope to get more advanced with time and experience. I also have a layer of gravel, a thin layer of charcoal, then the soil...am I missing anything? Thanks!

Eileen

I am researching about Wardian case/ terrarium and how it works but couldn't find it off the net and I have to draw a diagrams of how it works, so anybody knows in detail how it works and it will be helpful if there is a link or books which can help me find what I need. Thank you so much.

Given that the right amount of both photo-synthesizers and respirators are contained in the same terrarium, it can sustain itself indefinitely. Experiments have been done with a mouse and a plant together in a jar where the mouse lived for a while but I don't know exactly how long. This is connected to Darwin's theory of competition for survival. The populations of any species are always balanced in the world because of this and would be in a terrarium. Although the respirators may breed or grow faster than the synthesizers grow, they will eventually use up all the oxygen and a few of them will die, keeping the species at a certain population. On the other hand, if the synthesizers grow more, they could be eaten by the animal to create more CO2 and animals. Equilibrium will always be reached, unless of course the animals or plants all die. There are companies that sell small glass orbs that are completely sealed and contain only a small amount of sand, water, live shrimp or crustaceans, and some algae or bacteria that creates oxygen. These can sustain themselves for many years before the shrimp all die, probably from contamination from their own dead bodies. But, it is much easier with an air terrarium where you can have any number of different oxygen producers and CO2 producers living together who will all balance each other. You can even have ones that do both like bacteria.

I use a screen top for my carnivorous plant terrarium and keep about 1 inch of distilled water at the bottom, is this a good system?

This isn't a good place to ask. Very old thread. Start a new thread.