How small is small?
Was the small fish with other maroons or by itself?
When the large maroon attacks, does the small fish fight back?
Or does it hide, or shimmy?
I introduced my smaller juvi carefully. By putting it in a specimin container with holes and putting it bu my females anemone for 1 1/2 days.
My female attacked the container very badly, but my juvi was safe.
After it escaped (yeah, shotty lid) My juvi had all its fins bittin, and was chased about 1 whole day. After that it submitted everytime it was chased and she would stop short of biting it.
If your pretty sure the new fish you added isent a female. just let things play out. the biggest mistake people make is getting scared of what they are seeing and pulling the fish prematurely
dont pull out the new fish unless your really sure its going to die without your intervention. if the new one fights back and shows no sign of submitting, take it back and hold off until you can find a baby