Engineer Goby wont eat?

[PowderKat]

Can someone help me please?  My Engineer Goby hasn't eaten in 3 days and is lethargic.  I belive it is caused by an increasingly agressive Velvet Damsel.   His tail looks like it has been nipped at.  I moved the velvet today to a 55 gallon tank with an arrow crab and a bunch of snails and hermits to give him some relief.   Now,  Tonight after lights out he is swimming back and forth in front of tank (24g Nano)  and floating aimlessly around the tank with the current every once in a while.  Is he sick? Or is he just stressed and needs to be in a larger tank ( which I just found out with research) ?   Any help would be appreciated.   By the way... Im the mom who inherited the 2 tanks from the college student.  I worship the gods of saltwater tanks.  Thanks