You Don’t need to water at all. (At least if needed).
It should be moist all the time, the moisture will be the water for your plants.
Closed terrariums require high amounts of light, so keep them in a bright spot but out of direct sunlight as this could cause the contents to overheat. Similarly, keep your terrarium away from radiators or other heat sources that could cause overheating.
How often should I mist my terrarium?
You can also mist your air plant 2-3X per week but again make sure they are not sitting in water. After watering, leaves will be stiffer as they are full of water. When in need of water, the leaves will feel softer and lighter.
Closed Terrariums are low maintenance for the most part but we do have some suggestions to keep your terrarium long-lasting and healthy. If you choose to grow ferns, trim leaves to prevent them from overgrowing. … If you have a closed terrarium, you may want to remove the lid every now and then to let in some fresh air.