I would like to recommend you look into some type of way to create airflow inside your tank.
Many vivs have a low and high ventilated area to allow air flow in and then expel usually from the top. Tree Frogs usually should be provided some air circulation.

I have seen this from Zoo Med which may work and there are also some good topics on DIY fans using a fan from a computer.
Aquarium Cooling Fans: Zoo Med Aqua Cool Aquarium Cooling Fan AA-13