12x18 isn't really a "home" for any species of hylid. Tree frogs need lots of room, and 12x18 is just too small, especially if you have a background etc. in there. With a background, that 12x18 becomes 10x16 or smaller.

Backgrounds are nifty and stuff, but they effectively decrease the tank volume, hence why I do not like backgrounds.

I had some Litoria when I was about 14 and they were in a 36x36x36, and that tank was too small!