From Quake Wiki
"Disgusting little critters who dish it out, but can't take it."
If Rotfishes are even a concern, let them get moderately close and kill them with a shot from the Double-Barrelled Shotgun, that will take care of them most likely.
"Player was fed to the Rotfish"
|Monsters from Quake|
|Chthon | Death Knight | Enforcer | Fiend | Grunt | Knight | Ogre | Rotfish | Rottweiler | Scrag | Shambler | Shub-Niggurath | Spawn | Vore | Zombie|