ocellaris vs percula

[meiyouwenti]

I am just replacing an Amphiprion ocellaris but I think that I got an Amphiprion percula in error...The two fish that I have don't exhibit much colour differences (the percula doesn't have really darker bands than the other) and they don't stay still long enough for me to count whether or not they have 10 or 11 rays in their dorsal fin...How can I determine which one is which now? If one is more agressive toward the other can I assume that that one is the percula (they both are young and about the same size)? (I also assume that the fighting doesn't really start until they are a little older--these are only a few months old)...Is there any quick way I can tell which is the ocellaris and which is the percula? I obviously want to remove one and replace it with the correct species...Thanks