I also voted for "Bigger". I have a lone one in a 13 Gallon tall tank and I think it's getting too small as it has grown up. A 29 Gallon tall is in the works at which point I will consider getting another american green treefrog*.

Any old 10 gallon aquarium (with a secure lid) should be fine for a quarantine tank. It's only for 1 or 2 months. If you are getting them from the same place and putting them in an empty tank on their own (which is hopefully the case), I don't think a quarantine period is necessary.


*You are talking about American green treefrogs (Hyla cinerea) and not Australian Green Treefrogs (aka Whites, Dumpy, or Litoria caerulea) which are a fair bit larger?