Dark beer, what water?

l'd like to learn more and get better every time I brew, so now I'm trying to get some imput on water for an oatmeal stout which I'm brewing tomorow. I've been using bottled spring water for my brews lately, but am reading that maybe dark beers work better with different "hardness" of water than pale ales. What do you guys think?

Are you brewing AG? If not, it won't matter. If you are, dark malts can lower the pH of soft water below the optimal range of 5.2-5.4 in which case you would add a mineral that will raise the pH of the mash. I wouldn't do anything to the water unless you know the mineral content of it and have the ability to check the pH of your mash.

Edit: Actually, I shouldn't say it won't matter for non-AG, but you don't have to worry about the mash pH for a non-AG batch. Certain minerals can affect things like the flavors of the hops, but for a stout I wouldn't worry too much.

The Baron is right of course. One thing he didn't mention is that it's generally easier to brew dark beers, since a) Most of the water in N.A. is on the hard side, which is good for darkies for mash pH reasons and, 2) It's way easier to attain hard water through mineral additions than to attain soft water through mineral subtractions.