Help on care for brown tree frog?

I found him in back concrete back and I don't know how he got there but there are no water within 5 mile range except for some pond. I hap a backyard turtle pond But I'm afraid that the turtle might eat him so should I release him back to my concrete back yard with he going to be eaten my lot of bird because near where i live I saw stork, heron, crow, finches, robin and more and those bird come to take bath in turtle pond ( when the turtle not in the water) so should I keep him or release him back. and if I keep him please tell me how to care for the frog like what size is the cage for how much water or what does he eat like that. and if you tell me to release him give good reason and he only smaller than a thump.