Second clown?

[Whatigot]

I had the same scenario a while back and I just took the larger perc out of the main tank and put her in a quarantine at the same time as I added her new friend who was about 1/2 the size to the quarantine.
I left them in quarantine together and then put them both back into the main tank after about a week.

They paired up after that and were insepreable, though I might have just gotten lucky...