[rlcline76]

I apologize for not knowing much about your tank history.
What kind of goby do you have and how long have you had it? Gobies can be quite disease resistant but I QT them all the same because I have lost a few to illness. Lost them during a marine velvet episode (this is why I QT, because I messed up) so they can get sick...and depending on where this goby came from, environmentally, could be asymptomatic. I humor all sorts of possibilities.