I find that using liquifry is not ideal for livebearer fry. They are born pretty developed, and I put mine straight onto crushed flake with no problems. I know some people who use liquifry#2 and swear by it but I have never had any trouble raising them on quality flake food. I get a pinch of it, put it in a medicine cup or other small container, get an eyedropper and squirt some tank water onto it. Then I suck it in and out of the eyedropper until the pieces of flake become very small. In this form it also sinks. You don't need very much.
When the guppy is ready to drop, she will 'square off' and not look fatter in the front than in the back. She will look square from behind and her sides will bulge from above. She will also hide behind or under objects, act antisocial and may refuse food. Her size at that point is the only real indicator of how big the drop will be until the fry arrive. It can also be hard to tell exactly when a fish will drop. One of my platies, I could have sworn would drop within two days. She held on two weeks and then dropped 85 fry. Big female guppies can have over 100 fry, but this is rare. 20-50 is normal. Young females may only have three or four. How big is she?
If you want to raise the fry as feeders you've got about six months to wait. I suppose if you really wanted to raise fry as feeders (or had the space/time/money to do this) you'd be buying in livebearers and not minnows. 50 fry when they are 3/4 grown take up a lot of space (as I found the hard way, you can't save them all.) Will your LFS take them or have you got a predatory fish a bit smaller than the oscar?
