IMO you really dont need a hydrometer. Unless you buy an expensive one that you can calibrate yourself, they are pretty inaccurate with high humidity.
It's pretty easy to gauge by eye if you're humid enough. There should be some condensation on the sides of the bin, but not dripping wet.
If you've got wet perlite on the bottom, your FC doesnt have a ridiculous amount of holes,and you're misting daily, you'll be fine, especially with a casing.
Edited by Deleena24, 13 March 2019 - 02:18 PM.