Will mold grow within my bonsai greenhouse? I have tried previously to use items like cup jars as miniature...

I have tried previously to use items like cup jars as miniature greenhouses to grow plants. However, every time since it be moist inside the "greenhouse," mold began to grow inside.

My ask is regarding a plastic shoulder bag greenhouse I constructed to winter my bonsai tree in. I be wondering if anyone could tell me how to prevent mold growth inside the greenhouse while still retaining moisture and steam so that the plant will not freeze or dry out.

Thank you for your help.
Mike c electricity?
Answers:    When the mold begin to form, clean it next to a mixture of bleach and water. Check the bleach bottle for a proper mixture. You may want to read the Bonsai Care page of my site:
http://www.american-bonsai.com
Spider Question?
use brackish?