Infection on diamond goby!!!!

[Riley]

My brother called me emergency style earlier about his fish so i am here looking at it.. I do not have a cluuuuue what is going on.. Hope someone can help my brother out!

 

[Innovator]

Have seen something like this in other fish where progression leads to complete tail fall-off. I'm not saying that's what this is, but it looks very similar. Only thing that reasonably worked for us was Nitrofurazone at 3.5mg/L (use QT tank).