I caught 5 babies in my tank on Tuesday morning, (they tend to birth in early hrs apparently!) by netting and popping straight into the breeder tank. Mine, like yours I guess floats in the main tank. I didnt want to stress my molly mum out either (silver molly) infact, having studied the main culprit this morning I think I am rubbish at spotting which is about to birth. The molly I 'thought' had given birth still has the gravid spot (easy cos she is silver) and the babies would appear to be a little darker than expected...... I guess the sneaky black molly is the mum and we have more to come from the silver one!!
Be aware that the fry are mucky little fish and the breeder tank floor in mine was quite grubby within a few days.... I just used a sponge and cleaned it up.... the filter of the main tank must still work on the water circulating round the tank and I only keep them in the breeder tank for about 4 wks and then let them out in the main tank..... I reared my first babies successfully earlier last month and they are fine, and getting bigger every day.
Fx