Darts usually go into elaborate natural set-ups with many hours of construction and $$$ into materials, plants, etc. Now imagine that your newly arrived frogs are sick and you set them free in that set-up. If contaminated you would have to tear it all down, dispose of anything that can't be sterilized... a real nightmare.
Now let's go the opposite way. You plant your vivarium, introduce cleaners and let it stable out for a month or two. In the meantime you get your frogs and quarantine as per this excellent thread by Lynn: http://www.frogforum.net/general-dis...uarantine.html. Period should be a minimun of 30 days, with many keepers doing double that with 2 negative fecals 2 weeks apart.
You are looking for any ailment signs like: runny feces, lethargy or abnormal behavior, slow feeding response, anything that does not look like a healthy frog. Once quarantine is done then you introduce your frogs to their permanent enclosure with little to no risk it will become contaminated. Good luck!