I have a very small pond in my garden and every spring frogs and toads come to spawn. I even rescued a frog doing a very good 'ice age' impression this spring, frozen into the ice after a hard frost. They certainly do keep the slugs at bay. I also try to grow plants that slugs and snail don't like, lavender, lambs ears, astilbe, ferns etc. I have tried to encourage as much wildlife as possible into my garden and have lots of bird feeders, sun flowers, poached egg plants, buddlia bushes etc, and although some things do look a bit 'mauled' I feel happy to let nature take care of the garden without the use of chemicals.