Yes, its six gallons. I really don't think its over stocked. Its one square inch of fish per gallon. The betta is one square inch, 5 tetras are one square inch, other 5 tetras another square inch, and two frogs are one square inch (though, now I'm down to one). A square inch is a 3 dimensional box, not a 2 dimensional square. That said, I am technically using up 4 gallons and have two gallons to spare. Since there is a lot of controversy about how much space a betta needs, we can say he has two more gallons, for a total of six.
I think I may have solved the problem, though. Both the frogs and tetras are fairly new. To compensate the fact that I'm unfamiliar with how much to feed them, I was putting extra food in the tank (esp for the frogs) and not removing it. I was feeding the frogs these teeny pellet things for small frogs. They seemed to like them, but the stuff they didn't eat disolved in the tank like sand.
So I can do daily water changes without any problems?