The resident mantises, both nymphs awaiting sale or adoption and the permanent residents I keep as breeders or pets, live in fairly similar conditions that vary mostly with size.
My primary storage of newly hatched nymphs is in what I lovingly refer to as the Apartment Block, a series of small boxes that stack and are magnetized to a wall shelf. These boxes contain all the necessities of young nymphs while still being clear and allowing quick viewing to do morning and nightly checks. This way I am also able to tell young nymphs apart through a spreadsheet and numbering system so I can keep an eye on who is eating regularly and who has molted recently so that there’s no mishaps during shipping.
There’s currently space for 135 nymphs between the two apartment blocks that I have built. I do not let my stores of nymphs exceed this number so I can ensure that I can care for them all.
Older nymphs and mantises I intend to keep for breeding or as pets go into two other systems. First are the condos, enclosures with two units side-by-side where older nymphs or small adults live out their lives.
These mantises are kept side-by-side with those of their own species and while I’ve occasionally caught them watching each other through the plastic divider, I’ve never had issues with attempting to attack each other or injuring themselves on the plastic. The condos are stacked and secured to the wall with magnets so there’s no change of them falling over.
Additionally I have some single units for slightly larger species I refer to as Townhouses. These offer a bit more space and only house one mantis at a time. They do not stack for safety reasons (although they could if they had a proper racking unit like the condos or apartments).