Rts Is Picking On Other Fish

[D4N]

my RTS is picking on the ohter fish apart from my yoyo loach which is the smallest fish in the tank. so all the fish are hiding which is 2 bannded leoprinus 2 pictus cat fish
RTS is hinding nither is the yoyo loach

anything i can do to stop the shark from thinking he is boss!

 

[WILDER]

How big is the tank and does the shark have plenty of territory and caves.
It's there nature i'm afraid.