if you weren't going to feed out the nymphs, I would just leave them be in the substrate. As long as you feed them and give them the proper moisture, they should grow fast. My orange heads are overpopulating my container, as are my discoids and 'dubias. I couldn't be happier with the progress my colonies are having; I am still holding off on feeding out until I have an obsene amount, for I've got a bunch of hungry monitor lizards, who eat a S___tload of insects everyday. I am trying on working on a formula to give me an understanding of how many adults I would need to properly supply a constant supply of roaches to feed out. I hope I can remember some of the calculus I've taken in the past.... anyways, congrats with the babies!..
bm
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