As a general rule of thumb a frog should be offered no less than 10G of space to live in (some frogs such as pacman frogs don't fall under this rule). a 12x12x18 tank is roughly 11 gallons. Depending on the type of frog you are interested in and how you plan to setup the vivarium you will most likely loose at least 5 inches in height and 1 to 2 inches of depth. effectively turning the tank into a 12x11x13 tank of usable space which equals roughly 7 gallons of usable space.

With all that out of the way it is my personal opinion and choice to not house frogs in a tank this size, unless it was going to be on a strictly short term situation. Such as a quarantine tank/hospital tank. You can get your hands on a 18x18x24 tank from exo terra for around $110 and can easily house a pair of dart frogs or tree frogs in it.


Oh and Welcome to the Forum!!