here's some info I saved from when I asked the same question: this is bits and bobs put together off these forums and off sites on the net. The female is plumper than the male. But you've probly already figured that outNeons are voracious egg eaters. Remove the adults within hours after spawning. You can try using a coarse mesh at the bottom of the tank, some 1" off the bottom or so, to let the eggs fall through out of reach of the adults
snails eat eggs. the water should be stertilized by boiling for twenty minutes.temperature should be 75-78°f for the spawning. Rain water would be the best for this is you can gather it. Once you choose the male and female put the into the breeding tank. Use a dim light or cover the aquarium with a sheet to dim the sun's light. If your lucky, they'll start breeding the next morning. The eggs are about the size of a grain of sand and practically invisable. This is why you can't have gravel or sand. The eggs fall at random and will be lost if fallen on any gravel. Once the spawning is over and the eggs are laid, the female should be removed first for she will eat them. The male will chase here around the yank to prevent this.
Breeding Neon Tetras: Difficult. Use a heavily planted tank to reduce light levels. Use one breeding pair at a time. The parents will eat their eggs so remove parents after spawning. Keep tank dark. Young neons are very sensitive to light, until their eyes completely develop.
Fry should hatch after 24-36 hours and live on egg yolk sacs for first 4-5 days
.The powerfilters will likely suck all the newborn fry out, so use box or sponge filters. .
The eggs hatch in about a day. After the fry are free-swimming in about four to five days, they can be fed strained egg yolk, infusuria, other microscopic live foods, or Liquifry (which is mostly yolk). Provide subtle lighting over the tank once the fry are swimming so they can see their food. Often, some fry will not survive.
stripe on females is supposedly crooked while on males it is supposedly straight. Although this may generally be true I have seen males that I reckon have crooked stripes and I have seen females that I think have straight stripes
When breeding you need to keep themextremely well-fed