For me, I am not particularly trying to spawn anything. Conditions just seem to be right for the serpaes in this particular tank. The tank is so thick and dense that the egg-eating cories (plus three ancistrus - don't think they'd turn them down) don't seem to find the fry.
If I was trying to breed them specifically I would definitely set up a couple of species tank, one for the adults and one for the fry. I did not realize that about the lights-out factor, Brian - good to know.
When it comes to fish like N. brichardi and kribensis, for instance, you are definitely going to have an easier time in a species only tank. Kribs and brichardi both are extremely intolerant of other fish around at spawning time, and they will make life miserable in the tank. I'd probably do the same for angels, and give the parents 3-4 spawns to see if they can handle getting the eggs to free swimming stage - some can and some just can't get it done.