African clawed frogs are like the big meanie version of the dwarf frogs. Clawed frogs look a lot more "beefy" than dwarf frogs. They will also eat anything they can put into their mouth. Dwarf frogs are a lot more timid with their food in this sense.
I recommend at least 2 gallons per frog. I also recommend at least 5 frogs. Like the original poster said, they are social and prefer groups. if you don't have a heavily planted tank ("real" plants, not fake plants) give them a cave or two for decoration, they like the cozy darkness and shelter it can provide. My own frogs, we have a 20 gallon tank, but they still like to pile on each other.