Is a 20 long aquarium, suitable for establishing a dart frog habitat?

Another way for them to get water is to get a water holding plant. Also, If you gaet dart frogs then your substrate should be a live piece of moss, but im sure you know that. you should house them in the deli cup you brought them home in before putting them in. make sure there isn't too much still water, because these are terrestriial frogs. you shouldnt put the frogs in unitl getting the false bottom, plants etc,etc. Other than that, a 20 gallon long would be like heaven for them. you could house a breeding trio.