Ive had 3 different sharks, the red tail, albino, and silver...And I have had to part with the red and albino as they are very territorial! Every time a fish went anywhere near it, they chased them away and it was getting annoying as most of my fish stayed up the 1 end to get away from them!
But the silver I have now, although only a youngster, are very easy going fish, dont give any of my other fish any grief, they just get on with swimming and eating