Thanks for submitting this interesting observation. I would add to Anke-Maria's comment another question - can the frogs climb out of the water bowl? If it has slippery sides terrestrial frogs like these may drown. The climbing rock needs to come up flush with the top of the water bowl. Also, some rocks could be placed at the edge of the water mains box allowing then to climb out (or does it have a lip around it). Other wise this could be functioning like a trap. As i am sure you will know, water that is not kept clean can go rancid - very quickly killing frogs. Looks like a few species here (mostly Limnodynastes species and perhaps Crinia - no Litoria peronii that i could see).