There’s possibility of aggression but it’s slim as it’s just one and you are introducing multiple new ones . Are the newer ones significantly smaller than your existing one ?
In cases like these where I introduce anthiss to an already established group , acclimation boxes are of utmost importance .
I have had great luck in keeping the new ones in acclimation box for upto 2 weeks to let them still interact and study the aggression of the alpha male .
Once I reversed it and caught my alpha lyretail and put him in the acclimation box for a day after releasing the new ones .worked like a charm !
Regards,
Abhishek