Wendi has a really good point about adding seeding material. Think of your aquarium as an emergency situation, and the seed material is the fireman and paramedics. If you can get enough (it'd take a lot for a 55 gallon with that many fish), it can basically make your tank behave like it's cycled. If it was me, I'd go to every lfs near me and beg, plead and steal (well, maybe don't steal) for anything they can give you. Used filter media, gravel from an established tank, rocks, plants... Basically everything. Like I said, it'd take a lot of material to instantly fix the problem, but anything you can get will help immensely. Even a single used filter would help the process along much faster.
*after reading this back I just want to make sure it's clear that no matter what you add, the pwc's, constant monitoring, etc... are all still necessary to resolve the issue. The best course of action would be to go back to where you got the fish and talk to the manager. See if you can return the fish since their employee acted extremely inappropriately by selling you all those fish with no questions asked. The employee might not care, but there's many of us on this site that actually value fish as living things and hate to see them tortured because an ignorant, untrained employee didnt care to ask a couple questions that he should have been trained to ask.