Do you realize that adult African Clawed frog get up to 8 inches long? I have seen one female that reached 10 inches.
I had 3 adults years ago, and kept them in a 100
gal. aquarium set up about 3/4 full of water with rocks and logs built up to provide a shallow area theat made up about 1/3 of the tank.
The other 2/3's of the tank were about 20 inches deep in water.
Are you going to get babies and raise them? If os, then a small aquarium is ok, and set it up like I said above. These are strictly aquatic frogs and do not need a land area.
Here is a link to some more general care for these frogs:
African Clawed Forg Care
Good Luck!
[addsig]