Well, increasing the humidity is probably the only benefit, but it's a huge one, especially when you're dealing with tropical plants and animals, whose very survival may depend on high enough humidity levels. However, you should find out if this is a warm mist or a cool mist humidifier. The cool mist models become excellent breeding grounds for bacteria very quickly, and must be cleaned regularly. And yes, this is true even if you are using UV sterilized water. They can be very bad for your health and your animal's health, so make sure you clean it weekly at a minimum if it's a cool mist one. Warm mist still needs to be cleaned once in a while, but not anywhere near as often as cool mist ones.

its a cool and a warm mist humidifier and it has silver ionic technology that prevents the growth of bactiria what ever that means I already have a misting system so what do you thing is better warm or cool mist?

I would be wary of something that was designed to kill bacteria chemically - there is a good chance it will be harmful to the plants as well (if not directly, then by killing helpful bacteria)

Warm mist is better by far. And whatever this 'silver ionic technology' does, you'll still need to clean it regularly. I'd phone the company and ask for an explanation, just so you know it won't harm your plants or animals.

The ultrasonic humidifier is what you want for terrarium use. The silver ionic system shouldn't hurt your animals or plants, but only prevents a buildup of anaerobic bacteria in the reservoir. Colloidal and ionic silver is an old remedy for a variety of systemic bacterial infections, and is toxic only in heavy doses. I doubt you'll see those types of doses in the humidifier. Good luck!

the silver ionic thing is probably a small negative ion/ ozone generator ozone is what they use in some water treatment plants. as long as it doesn't make high amounts of it it will be fine and i doubt it will make super high amounts of ozone