My 10 gallon tank right now currently has 2 mollies and 1 platty the water is slightly salted to accomodate the mollies and the current water temperature is about 80 degrees. This weekend I was planning on a goldfish at petsmart since they're on sale for only $1. Will the goldfish get alone with my current fish right now? Will there be any potential problems in the future? Thanks in advance for the help.