Unfortunately no, leaving water with chloramines out will not allow the chloramines to evaporate over time. They must be broken down through the use of various chemicals, or by being run through a filtration system that uses activated carbon. Technically you could load up a filter with activated carbon and filter the bucket of water and that would break up the chloramine bond and get rid of the chlorine. However, it would still leave the ammonia to deal with. Yes you could get bio-filtration going there to eat the ammonia, but then you have nitrite to deal with. Back to the bio filter to eat the nitrite, but then you have nitrate to deal with. And we all know how long all of that can take
. So you are better off with using a chemical to break up the bond, and then depending on the amount of chloramines in your water will determine if you will have a lot of ammonia left over (i.e. more then your bio-filtration can handle) in which case depending on your pH you might need something like Amquel+ or Prime. Yes it's confusing, but if you like that sort of thing...
check out this article. Ignore the "reef" parts of it (which aren't mentioned that much anyway) and it's got a lot of interesting information in it.
Similar Aquarium Fish Forum Threads
) then it won't do anything (or at least not much) as you can't break up the chloramine bond just by letting the water age. But this would certainly work well for the OP since he doesn't seem to have chloramines in his water either.