Bullfrogs should be in a minimum of 10 gallons as babies, and take about 2 years to reach adulthood, which they need 20 gallons for the first frog and a additional 5 per extra frog. You can feed them algae wafers, shrimp pellets, flakes, bloodworms dried or frozen, and frozen brine shrimp. A light, filtration and hiding places also are preferred, dont release it into the wild.
I would be worried about them getting food and making sure they were free of illnesses, and if they can reach the surface for air that easily, but im not an expert on frogs so sorry haha.