Hello,
1. How often should I dust prey with Calcium/vitamin supplement?
calcium daily -( vits less often) I have a rotating schedule: .....Rapashy ( which has vits in it ) ,repcal vits, and repcal ( cal w/vit D)
2. Would a Reptifogger be good for keeping humidity in the tank?
Yes ! But....Sorry ....I have never used this product- ( I only have experience w/ mist king)
3.Should I purchase another poison dart frog to go in there, and if so, should I do the same species, or can I do another one?
Yes ...same species! Leucs are quite comfortable in small groups. Mixing dart species should only be attempted by very experienced dart frog keepers. If done , only certain species are mixed. A very, very large enclosure is needed.
4. What size tank is recommended for a successful vivarium?
This really depends on the species. You can't go wrong with a 24" high enclosure.
5.What else should I do to improve my 20 gal. tank?
Turn it vertically ?
Consider a layered substrate...."naturalistic tropical vivarium": keep in mind this takes up 5-6 " of ( height) space
Naturalistic Vivarium Substrates | Reptile and Amphibian Substrates | Josh's Frogs
Lynn