Yes what vincor said is true. If you can't get a breeding tank like me......just improvised with the smaller version of plastic sieve which our mothers used to wash vegies and to drain it from the wash water and float it in your tank with the pregnant female in it. Make sure the holes are small enough to retain your female and big enough for the fries to escape.

Make sure there's the gravid spot to ensure the female is really pregnant. Otherwise she might be bloated or housing some worms in her belly. The gravid spot is fairly easy to spot with grey bodies. I have some difficulties with shall I say platinum bodies which is quite transparent. People say you'll be able to see through but the fact is even the fries are more transparent than the mother. So where's the gravid spot!!! Haha some points to ponder.....