Test your water. I don't know why you would put goldfish in?
By putting goldfish in there, you are exposing your fish that are already established to any number of different diseases and parasites. Take the goldfish back, clean the tank thoroughly, and when you are done, fill up the new tank with water, dechlorinate it, temperature match it to your other tank, and put the old fish in the new tank, with all old filters from old tank. Done.