Dace and everybody else - warning! Please read forum terms of use before posting further.
and just to clarify - "happy " in a hobby means not stressed out animal and that is what any responsible frog owner need to try to achieve. Snakes in small tubs are not "happy", but unlike frogs they are more forgiving to husbandry mistakes and similar to frog hobby, responsible snake owners are keeping their snakes in adequate enclosures (tubs).
To OP - you haven't specified the dimensions of the tank, but by the looks of it, it is not suitable for tree frogs, sorry. Tree frogs need space, the bigger the better and if you could provide the size of the tank we could advice you better.