Succulent/cacti Based Gardens
Open mini gardens are not terrariums, they do not create there own rain cycle and require regular but low maintenance care from you.
Succulents require little maintenance,
Succulents and cacti like plenty of bright light, they do well on a window ledge that gets an hour or two of morning direct sun or late afternoon direct sun, but definitely not the hot midday sun. They enjoy warm to hot dry air and will suffer in humid damp air especially if light is limited.
Succulent and cacti gardens do require watering, but very minimal watering, always allowing the soil to dry out between watering. Spray lightly every week or so depending on how fast your garden dries, slightly increasing water amount when weather becomes warmer and slightly decreasing when cooler. Spray around the base of the succulent/cacti not the leaves or body or the cacti, letting water sit on the cacti or succulents can create rot. If you notice the leaves shrivelling, it may require more water.
Pruning and cleaning.
To discourage rot, it's best to remove fallen leaves from the garden. Clean the glass with a damp cloth. It is also good to allow the garden to receive fresh air from open window when possible.