Get a Zoo Med Naturalistic Terrarium 12"x12"x18" or a Exo-Terra of that size maybe a little wider, but 18 inch height should be high enough. Like was said by members above, Tree Frogs need tall tanks so they can climb up high. This is where they feel secure and buy a hygrometer so you know how high humidity is in the tank. Even though the ambient room humidity may be fine it may not be the same within the tank because the tank will have a seperate little microclimate that needs to be maintained and monitored.