The tanks that you expect to be fishing a lot of babies out of to sell/ship you probably want to keep sparsely decorated/planted for obvious reasons.
That said a lot of fish seem to spawn better and have better survival rates in very mature tank with a lot of bio-film and microfauna (basically heavily planted that and let run free).
I am not sure that this applies to the commonly (easily) bred fish though. So many different breeding habits/practices, etc.
I definitely agree with whoever suggested using the extra real estate in all of those tanks to grow out some various mosses. You have the room already so tossing mesh tiles and waiting for the moss to grow won't really be a problem since it is just a bonus for you.
Plus mosses are great for fish fry usually.