What is condensation and do I need one in Terrarium ?
Condensation represents rain cycle in a terrarium.
Condensation forms when the air inside the bottle is cooler than the air outside of it. This results in a lower saturation point for the air and liquid, which displays as condensation on the glass inside the bottle. This is very common, especially if you have your bottles sitting on a counter or shelf, as the temperature surrounding the bottle will fluctuate as your air conditioner or heating unit turns on and off. Condensation is also a pretty good sign that the seal on that bottle is tight. The tighter the seal, the harder it is for the air inside it to escape, thereby creating the condensation.
The condensation comes from temperature cycling inside and outside the bottle. If the water in the bottle reaches a higher temperature than the outside of the bottle, then vapor in the bottle will become saturated relative to the inner surface temperature and you’ll get condensation. This can happen when the bottle temperature lags behind in a thermal cycle (e.g. a car cooling in the evening) or if the bottle is exposed to a heat source like sunlight
How much condensation is enough ?
Ideally, condensation in limited amount is recommended. Condensation typically should occur at a particular time in a day. No condensation is not good. Too much condensation may signify over watering and obscures the view of terrarium.
How much should you water ?
The key to a successful terrarium is condensation. Inside the glass, the water cycle is happening and if water levels are correct, condensation should form on one side of the terrarium about once a day. If no condensation forms on the inside of the terrarium, add a couple of tablespoons of water a day until it does. Check to see that plants are getting enough light. (Inadequate light will prevent the cycle from starting.) If condensation forms on more than 1/3 of the glass, wipe it off with a paper towel and seal the top again. Do not leave it open to dry. Plants that like high humidity will suffer if you leave it open. If excess condensation continues, repeat daily until only 1/3 condenses. When it is right, put the cover on and leave it in good light. Give it a spray of water or a few tablespoons every few months, or when condensation stops. It is always best to err on the side of less water; it is more difficult to remove water from a terrarium than it is to add to it