Hey Schweinl,
you could do it inside the script of your fish. Deleting a nod is done with queue_free(). You can do the same from everywhere else too, in case your fish doesn't have a script.
But your code looks strange. You are probably not doing FishClone = add_child(Fish)
. At least there is no sense in it. add_child()
returns nothing so FishClone is empty.
Hope it helps.