That's it ^^^...humidity is a poor description IMO, yet its the most commonly used term. Worry less about the moisture in the air and more about moisture in the substrate. You do not need a hygrometer.I keep them in enclosures with cross ventilation to avoid mould or fungi. Then I add water to the substrate to keep it slightly moist. That´s pretty much it Oh, and I live in an area with very dry air, especially during winter.
I do something similar. I use syringes and inject water into the sub. I like your idea though, reminds me of dart frog tanks.For my P. metallica's adult enclosure, I buried a straw in the substrate so all I have to do is add water with a squeeze bottle and that works really well. Other than that, just use lots of sphagnum moss to avoid mold/retain moisture and make sure you have s decent amount of cross vent.
Appreciate it but for little ones i use the syrnge that comes w/baby medicine and for my larger enclosures i use the blunt syrnges my wife brings me home (she works in the medical field).I get some off of Amazon, and I order blunt tip "needles", aka liquid dispensers in the machinery sector. If you want name of vendor, let me know, they are a Mom/Pop outfit and really nice too.
This is the kind of thing which would benefit from first testing existing enclosures to see if they can maintain a high humidity. Elaborate constructions may be unnecessary.I don't keep any humid species, but have been considering enclosure design for them. Has anyone tried something similar to a vivarium setup with a false bottom? That is, a layer of clay balls covered with netting topped with substrate?
Conceivably with a foam backdrop you could carve out a space for a piece of 3/4" PVC (or any tube, really) that reaches down to the false bottom to add water as needed.