Brad,
I am afraid I don't agree with the others on this one. I have 2.1 Black Milks, and I love them. But I don't know that they are the best starter snake for you, Brad.
First off, although adults are dog tame, babies are typically squirmy little milksnakes.
Secondly, a 30 gallon tank is not a good size for a snake as large as a black milk. They need a tank more in the 55 gallon size (although keeping snakes in glass tanks is hard. It is difficult to keep clean).
I think a better choice would be a Mexican Black Kingsnake. A very similar looking species that doesn't get as large (around 4 feet), can be kept in a 30 gallon (long) tank, and they are docile easy to handle snakes. They are also about 1/3 the price of a Black Milksnake.
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Chris Harrison