Brett is right, You would need to modify the Exo Terras to make them escape proof for fruit flies. It isn't hard to do if that is the tank you are wanting. To replace the screen top just take the top of the new tank to a local glass company and tell them you want 1/8" thick glass cut to fit the top. I had a top cut for a 29G Long and a 40b tank at the same time and spent less than $20 on the glass total for both tanks. Dart frogs need near 100% humidity so no need to have any openings on the top. The air exchange that will happen when you open the doors to mist the plants or feed him is plenty.

One other thing you will want to start doing is setting up a new Fruit Fly culture each week. This will ensure you always have enough food for your Dart. The springtails will breed a lot and will also be eaten by your frog as a snack. You can put most of them in the new tank and put some in a breed container so you can ensure you always have Springtails to add back into the viv if you notice their numbers are declining.