Hi from UK

[Mentat]

Hello and welcome to FF Samantha! Would not place any new frogs in same enclosures as my established ones without a Quarantine period of at least 30 days to ensure they are healthy. A quarantine tank not need to be elaborate and is same as a hospital tank. As long as you provide a water dish, substrate of plain damp undecorated paper towels, and a couple fake plants to make them feel secure it should be OK. You've got FBT's for 8 years so presume you know all the basic stuff; but here is FF's excellent care article for your reading: Frog Forum - Fire-Bellied Toad Care and Breeding - Bombina orientalis and relatives .

After that period you can introduce the new frogs to your permanent enclosure as long as the younger frogs do not fit in the mouth of the older ones. Good luck !