I don't have actual experience in keeping these, but I would say that even as a wild frog and you wish to help him you could catch him and take him to the vet. Is the water in the little ponds de-chlorinated? If not then this is possibly the reason that he is ill. Lathargy and bloating are also signs of Toxing Out Syndrome which is usually cause by exposure to chemical in their water supply or fowled water.