When 1 fish chases the other for 3 minutes and the other hides>?

[NEMOOOOttttttttfinding]

i have many clown fish, one of my clowns keeps on chaseing the other, its beginning to bother me, the other thats getting chased always hides or runs off, whats the matter, Dominance? there the same size though, Pairing off and territory? advice
Im sorry he doesnt run off he swims off, lol!