[Rodrigo]

Saprolegnia is literally everywhere. Not technically a fungus anymore, by the way. It´s now in the class Oomycota.
I wouldn´t be concerned about the pressence of Saprolegnia (because as i say it´s everywhere anyway and should not be a concern for a healthy animal), but rather about the possibility of having introduced other patogens/parasites with the goldfish. They have been known to carry deseases to which axolotls are susceptible.