agree with the guys, vivarium + pacman = bad idea unfortunately, with the amount of waste they produce it doesn't matter what kind of filter you have, you will still need to change water every day ( well with a filter if a frog wasn't in a water at all i would probably go every second-third day) and substrate every month. 20 gal is way way too big if you're getting a baby. a water area gotta be shallow, no higher then a frogs chin, it is a matter of drowning, they don't swim at all.