1 1/2 - 2 gallons per frog

If you want to look into it further, here's a couple sites you can take a look at for more info... I used them before I bought mine
http://allaboutfrogs.org/info/mypets/dwarfs.htmlhttp://www.flippersandfins.net/ (this one has a good FAQ page and a whole forum full of frog owners LoL)
Enjoy! I must have looked at those pages a hundred times before getting my frogs LoL The pictures are so fun to look at

Be sure you read over them well... They do have a few special requirements, but it's nothing hard or spendy to meet.
Also, they aren't *really* active. Mine tend to be more active starting around late evening but they are not as busy as fish usually are still LoL
I'm off to bed. It's 1am here. I hope the links help you out