Welcome to the forum. African Clawed Frogs are nocturnal, not active during the day. And the frog needs some time to adjust to his new home. Are you providing enough places for the frog to hide? What are you keeping the water temperature at? What type of filter are you using? Most filters stress these frogs out due to vibrations in the water and African Clawed Frogs' sensory organs. Since you have him in a relatively small aquarium, I would consider frequent 100% water changes rather than using a filter.