yeah...the change in water chemistry can simulate a recent rain storm (natures water change), a period during which many fish species love to breed.
Hopefully dad is diligent and picks out the non-viable eggs. My male angel just stands by and watches the eggs diligently, also gets very angry if anybody (including the female) approaches them...even if half of them are non-viable. I was expecting to have trouble with them eating them all...quite the opposite.