UPDATE AT 3rd of september 2011, these ewingi tadpoles started developing back legs just after 4 weeks and its now 6 weeks after i found these eggs.
they are noticably not quite as active as when they were younger and seem to rest on the bottom more often, the water temp i have managed to keep at about 19 degrees during daylight hours (16 hous per day), the ph has stayed around 7.0, here they are at 6 weeks today :



if you cant see this try this link litoria ewingii tadpoles 6 weeks old back legs growing bigger - YouTube