Swordtail

I let this one 'ride' for a while, for Mickey to answer as Livebearers are his chosen field...but in case you did want a quick reply here is my advice:
All female Livebearers do not take kindly to being netted and moved close to 'birth-time' Swordtails are not as delicate in this matter as are female Mollies and Platies but delicate all the same. Livebearer females, moved when heavily gravid will often either give birth early or even abort their brood...I even had a female Molly die after trying to move it to 'safer' quarters.

So, if you plan to use a breeding tank my suggestion would be to move her as soon as possible, if she was already gravid when you bought her the chances are that birth is reasonably imminent.
If your breeding tank happens to be one of those netting ones be aware that larger fish, Angels especially, will 'suck' at the fry even though the mesh is between then and the Angels. Believe me, the 'suck' is very powerful, any fry given this treatment will either die or end up so deformed as to be of no use...also, Swordtails are not averse to eating their own young so my advice would be to remove her as soon after birth as is practicable.
As to evidence of how ready the female is...well, if you can manage to look down on the fish from above you will be able to see the 'stoutness of her better than from sideways on...also, the Gravid Spot (sort of triangular, above the Pelvic fins) becomes darker the closer to birth it becomes. So if the fish is good and stout and the 'spot' is nice and dark...don't delay !!! One last piece of advice, if at all possible trap her in your net and then, if using a breeding trap attempt to submerge the outer edge and try to 'steer' her into it...rather than lift her out in the net to transfer her (does this make sense? - I know what I'm trying to say, but it's hard to put it in words - sorry).
Good luck, let us all know how it goes.
John

Tony,
I can see you aren't happy with your female Swordtail in the smaller tank (my guess is that she was moved a bit too late, I, as I was trying to say yesterday, haven't had too much success with moving female livebearers too close to birth time) so I would suggest you let her back in into the main tank and let the fry take their chances.

Your little breeding tank wouldn't have been altogether the best idea anyway as the fry would have slipped through the slots and been in the tank proper anyhow...they'd have still had to take their chances anyway so my suggestion would be to release her and - if you can, get one of those 'net-type' breeding traps - you could then attempt to rescue some of the fry and let them grow up to a size where they can safely be released back with all the other fish. You might just have some unwanted attention from the Gouramis and other Swordtail adults, but I think some will survive the ordeal.
John