Introducing fish while there is an aggresive Tang

[SeaHorse_Fanatic]

Get some eggcrate material & build a large enclosure that can fit into the tank. Then place the new fish in there for 5-7 days. During that time, the Sailfin will try to attack it through the bars but by the end of the quarantine time, it should be used to the new fish. I have used this method very successfully in the past to get past that first few days of hyper-aggression. This gives the old fish a chance to smell, see & "taste" the new fish & get used to it being there. It's that first bit of time that most new fish get killed.

HTH,

Anthony