Well, I'm not sure
exactly what encouraged them to spawn, but i'll do my best
From my own obsevations, they seem to prefer temperatures around 22c- they're less colourful in coldwater tanks and not as active in higher temperatures. I've read that a large, cooler water change can encourage spawning but I haven't found that myself- I hadn't done a water change for over a week when this batch of fry appeared.
I saw a marked increase in fin displays and possible mating behaviour when I began feeding frozen foods regularly, although I didn't see any actual spawning until moving them into the river tank.
pH is about 6.6, with almost zero KH/GH, and I've got a lot of bogwood, so the water has a nice tea colour.
I've seen them spawning in the depths of my anubias a few times, and everything I've read agrees they like dense plants for spawning in.
When the fry hatch they stick to the sides near ther surface or hide among floating plants, so it was quite easy to scoop some into a breeder net. The fry don't seem to be temperature sensitive- I moved them from the breeder trap to an unheated tank where the temperature varied from 15 - 22c, depending on the weather.
In general, I'd say that lots of current and a moderate temp are the most impotant factors in keeping them happy, but I'm really not sure which factors are most important in encouraging spawning, hence the slightly rambling reply
I hope this has been of some help, and I'm sorry I can't give you a more definitive answer
