If you can't splurdge on a nursery tank, then I'd use. The 2litre way.
Cut in half
Cut slits small enough for the fry to not slip through
Take the top you cut off and make a circle the size of the opening and put it in with larger slints in it. This is for the babies to fall through. Secure it in place and you have your own fry catcher, of course you could always buy a breeders net...... LOL