I have successfully bred danio reiro (zebra danios) and discus fish. I am having problems breeding the neon tetras. What steps have you implemented to achieve neon tetras.
I have used the "spring freshet" style. This involves adding peat to RO water in a separate container (usually enough to do a 10%-15% water change every other day over the course of a 1 week period (you may have to do an additional week). The water should be room temperature to also aid in stimulating them to breed. If you have an overflow drain, this is much easier as you can simply just gravity feed the water into the tank.
This method has worked great for me on neons, black neons, numerous plecos and angels. Though I have also had the angels and clown plecos (peckolita sp.) breed by simply taking a handful of peat moss and spreading it over the surface of the tank.. The peat settles to the bottom shortly. This isn't as nice to look at, but easier to say the least.
As Anders stated above, the water quality is important. I have managed to breed neon tetras in aquarium by adding peat extract (Tetra Torumin) in the water, and also noticed that direct sunlight stimulated fish to spawn.