Hi,
I'm just a newbie here myself, but I recently had a bunch of unexpected mollie fry (still have about ten out of the original twenty or so). I asked and was told to try a turkey baster to catch the fry. The type of baster that is like a giant syringe, with a bulb at the top. Although all of my fry end up in the overflow box so they were rather easy to catch in such a small area (yes, I now have net around the weir). I bought a breeder net box which hangs inside the main tank, slurped up the fry and put them in the net. I crushed flakes and freeze dried blood worms which the fry loved. Once they got bigger than the adult fish's mouths, I let them free in the main tank. As the forum members will tell you, the fry need hiding places, such as lots of plants.
Good luck, they are fun to watch grow.
MissMelba
175 gallon with two panda cories (plan to get more soon), three black baloon mollies, two sunset platies, two orange wag tail platies, about ten black fry, and room for more fish