your tank takes 4-6 weeks to cycle, and that doesn't mean letting the filter run for that time. you need to dose ammonia to get the bacteria started and buy a test kit to monitor ammonia, nitrItes and nitrAte levels. now that you have the fish already, you might as well put them in (i hope you at least conditioned the water) to start a fish cycle, which is not recommended because it puts the fish through enormous stress because of elevated ammonia and nitrites.
a small bag contains very little DO (dissolved oxygen) for fish to breathe, especially in such tight quarters. waste will begin to build up and pretty soon, your WC's will start to die from stress and bad water quality. I had to do this to my BF tetras when i first got them. they were kept in the bag for around 24 hours, i ended up with 1 dead loss out of the initial 9.