Glenda just about had me sold on the cardinals on the weekend, Oceans has a few in right now but none of the literature they had (nor was their internet working) that would allow us to find out how to sex them so we could get a m/f pair. What I have found since though is that you cannot tell
It has been suggested that you buy 3 or more and find if two pair off and then remove the third before it is killed.
I've tried a manadrin before but it starved as I do not have a big enough pod poulation (nor a refugium to grow them)
I've also considered foxfish but my pansy side comes out as I am afraid of getting stung, or worse my daughter as she likes to stick her hands in the fishtank when I lift her up. (I created a monster becuase now when we go to the LFS's she is at just the right height when I carry her for her to stick her hands in every tank.
)