Cloudy water in acquarium?

I just purchased a TopFin 2 gallon acquarium with air pump, undergravel filter, and light hood. I placed acquarium pebbles on the bottom, a sea shell, and a silk plant in it along with the reccommended dosage of water dechlorinator. After running the pump for a day, a bought 2 african dwarf frogs. The first day, the water was very clear. Now, the 2nd day, the water is quite foggy. I have the light on for 12 hours and then turn it off for 12 on the acquarium. The frogs seem to still be doing fine, but what is causing the water to become so foggy so quickly? I provided my frogs with 3 shrimp pellets on the first day and it doesn't seem to be making the water cloudy.