Tadpole care?

Ok i have a pond near my house that has a ton of tadpoles in it. As an experiment i have taken 3 and they are in a half milk jug with the pond water in it. They have alge to eat ( i think thats what they eat) and i know not to put regular water in. But i want to to if im doing eveything right to keep them alive and also if my container in big enough, if not does anyone have any suggestions?