Most of the time its neutral at around 7. Fish don't really seem to mind and my L201's been spawning at 7.4 even.
The main sorts of things you are looking for is to get nitrates down and water very clean and wait for a low or storm event. All my plecos get excited when the barometer level drops.
Sometimes putting a ledge of slate or driftwood over the cave can help so the female can sit around the entrance under cover while she makes up her mind if she wants to go in or not.