Added a waterfall to my garden, want to add salamanders. Need advice please.?

Question:I've recently added a stream with 2 waterfalls into my garden. The total length of the feature is about 10 feet with one 8 inch and one 14 inch waterfall. I also have several flowers in the garden that get devoured by slugs. I've heard that salamanders eat slugs, so I was thinking about buying some from the local fish and pet store, but I wanted to know some details:

1) What kind would be good for the waterfall? It is turned on and flowing for 3 or 4 hours a day, otherwise I have it turned off. Can salamanders survive in or near it?

2) The garden is only about 150 sq. ft. How many should I buy?

3) Should I also run the waterfall at night to keep the salamanders hydrated?

4) Do they live in the water, or in the little crevices between the rocks, or in the soil?

I really don't know anything about this topic, so I would love your help!

Thanks!

Answers:
I am thinking that it won't take long for a couple of frogs to take up residence in your water feature. I would think that salamanders would just leave if they didn't like it there. If you go to the pond store, they can tell you whether salamanders would survive in or around water. But I promise you frogs will take care of your problem. If you build it, they will come.