Most of the terrariums are low water required. DO NOT over water, it will damage the root of the plant, and better spray watering for easy control. Like in nature, a terrarium likes rainwater or demineralized water (bottle of water) to feed. Better to avoid using tap water to extend your terrarium lifespan.
The enclosed terrariums - They are like a little ecosystem. The moisture will stay in the jar for a quite long time. Only spray water them when you don’t see the condensation on the wall of the glass.
The open terrariums - The natural airflow brings some moisture away. You need to spray them when the soil is dry.
The succulent terrariums - Generally require very low watering. Don't have to water until the leaves are getting wrinkled.
The air plants - Require a generous misting or soaking at least once a week with room temperature water. Air dry. Need air circulation, ideal to display in a wide-open terrarium or open stand.
Get a BRIGHT spot that receives plenty of INDIRECT light. If there is little natural light, artificial light can be a good source as well. Remember, the terrarium doesn’t like direct sunlight, it will kill them quickly. Please keep it away from the “hot spots”. The plants grow toward a light source, in order to keep them upright, turn your terrarium occasionally.
Regular clean the glass is necessary and please use non-toxic products to clean the terrarium interior if need it.
MOLD AND BUGS
Regularly check the soil, landscape, and plants for mold, if found it appears, remove the mold immediately.
Mold outbreak is the sign of too much water, simply open the lid, ventilate the container, it might stop the infection.
If half or more area is infected with mold, it is time to start over again.
No need to panic when you see the bugs / insects inside the terrarium, they are part of the ecosystem and actually help for the terrarium being healthy.