You can put them in a bowl or ice cream tub inside the tank.
To catch them try to scoop them in something, rather than a net...you can use the latter to chase them.
i used plastic cover from a cake )) its square shaped and floating great! also its transparent so you can see your fry clearly )But if you have a spare container(s) you could keep the fry in those (DIY if you have to).
With being in a 10G maybe there isn't that much difference. Most of the time I was observing, the fry were in the middle. At times over the past month there've been a lot of floating plants (larger duckweed), but it didn't seem to draw them up.Some notes about WCMM:
The babies tend to inhabit the upper areas of the water column and frequently like to shelter under large floating plants like Water Sprite and Salvinia. The babies will invariably be found near the water surface, even before becoming fully free swimming. They are really pretty at 3 to 8 weeks of age because they develop a bright neon green stripe which eventually dulls as they approach adulthood. A school of dozens of them at this age is really pretty.
I imagine 20 juveniles schooling must be a treat, they're so bright...Last summer about 20 new babies were accounted for. Well fed White Clouds can be quite fecund, and they don't normally feed on their eggs or fry like other egg layers.