Sexing Porcelain Anemone Crab

[syncro]

I figured that bottom piece detached into a flap (tail) only when the crab molted. I'll look at shrimp sexing info.

[syncro]

So it seems the best way to determine sex is to buy several and see if any pair up. Are the opposite sex fairly similar in looks? I've seen porcelains for sale with different sized spots and different color spots. How can I best be sure to get the same species?