Do you know what they were fighting about? Was it food time? Over a hidey house? It can help to emove the cause of the flash point. Was it over space? Was it a prober fight or justa bit of rubbling, chattering, threats etc?
If it was a full on fight it was lucky they didn't draw blood... and like Ellie and Kate I would be cautious incase things happened again and one of them got hurt. But since they seem to have settled down lets hope it was something and nothing but you do need to watch them very closely incase it happens again and as I say try and work out if there was any obvious reason. Have a towel ready to seperate them or you could get injured in the process of getting them apart.