With that many fishes in the 55g, I suspect you will be facing another ammonia jump soon...
Do you know anyone who owns a mature tank already? I'm afraid you are looking at alot of large water changes in the near future, or alternatively, take some of your fishes back...
Just as a comparison, I cycled my original 25g using only 3 platies and I went through daily water change (30%) for a month just to keep ammonia level in check...