Update on fry

Question
Welp, it's official. I had only one survivor of my .. litter? of swordtail fry.

"Lightning" is what my grandma named it. It looks like a female. When can I tell if it's a male?

It is in a breeder box inside the main tank. It is friendly towards me and when I come to feed it, it swims and follows my fingers.

It's almost half an inch long and is bright orange with a black tail.

So now I have in my tank a male orange platy, a female orange swordtail, 2 female beta fish, and 2 cory catfish (genders unknown.)

Can the platy and swordtail breed? I hope not. I bought different types of fish/same genders because I don't want them to breed. I don't know how to take care of baby fishes, but I am super excited about this one. I'm kinda glad there's only one.

How big should Lightning be before it can rejoin the main tank?

Answer
Technically, they can breed, but it's very rare, so no worries.

The baby should show signs of sexuality within the next month or so.  :)  If you don't see a pointy tail, it's not a boy.  Its sexual organ should also show by then.

He needs to be about an inch before introduction to the main aquarium.

I'm so sorry this took so long to answer.  I was away on vacation and forgot to turn off my All Experts profile while away.  Eek.  

Happy fish-keeping.