Hi Phillip J. Sorry to hear of your fish loss!! We have all lost many! Don't give up, keep learning!
Can you tell us how you "introduced" the fish. Can you discribe exactly what you did and how, step by step.
Also how big is your tank?
How long has it been set up?
Do you know your Ammonia, NitrIte, and NitrAte numbers? That's AM, NI, NA
Do you have a Liquid testing kit? or test strips that are not as reliable.
Also what temperature is your tank, and do you use a good de-chlorinator product?
Let us know if we can help figure out what happened.