HELP !!! fish dying in my 38gal

[Keen]

I went to Big Al's, and they told me that the disease I have in my tank is more than likely velvet, not ich. So I got this medication called rally for velvet, and started to medicate the fish. They also told me that a neon goby would help fight the infection as they tend to remove disease from other fish. hopefully the neon goby does not die before the velvet is removed.