For enclosed terrariums, you don't need to add water very often (approximately fortnightly to monthly). As a general rule, if you can see condensation in your enclosed terrarium on a warm day, there is no need to add more water. The terrariums with a cloche (e.g. Flamingo and Little Fig) require more water than the fully enclosed terrariums. It is important that the moss and top layer of soil remains damp at all time.