Actually Breeding Neons....
Isn't really all that difficult. As for most all fish, if you give them the proper enviroment and water conditions. They can be spawned successfully. One thing I've seen in the last few years. Are that a lot of the wild fish coming from South America go through a scanner, to check for contraband. And the radar used has been sterilizing a lot of the male fish. I have successfully spawned neons quite a few times, along with cardinal tetras. Both spawn the same.
If you're really interested in spawning them here's what I do.
First off, conditioning the fish is the most important part of spawning them. Water conditions in my tanks are, Soft and acidic. A dh of 2.O to 2.5 with a ph of 5.5 to 6.0. I also keep them at a temperture of around 76 to 79 degrees.
First you want to start to condition the fish on live food, I use brine shrimp nauplii, white worms and micro-worms. Also small new born daphnia will also be helpful to start conditioning.
When I notice my females are starting to get ripe with eggs, I start setting up my breeding tanks. A 5 or 10 gal. tank will serve the purpose. Neons are egg scatterers, and are also notorious egg eaters. They also spawn during the first part of the morning. So you want everything set up and ready when you introduce your fish to the breeding tank. Since neons scatter their eggs you want the breeding tank planted heavily. This will also help to hide some of the eggs, so the adults don't eat them. I use either java moss, or cured spanish moss. I also run a peat filter in the breeding tank, which helps lower the ph of the water.
When the fish are ready to be introduced to the breeding tank, the filter is removed. I always try and start my breeders on a Friday night. So Saturday morning I can be up and ready for them when they spawn.
I use 2 to 3 male per female when spawning. After they have spawned the adult fish "NEED" to be removed from the tank. The females are setup in a tank of there own until they're ready to go back into their regular tank.
I will then just run a small airstone in the tank for the fry. "DO NOT PUT ANY KIND OF FILTRATION INTO THE TANK." In about 3 days you should start seeing the fry free swimming. Believe me they are extremely small. They actually look like small slivers of glass. This is when you want to start their first feedings. You'll need to start the fry out on infusoria first, until they're big enough to be fed on brine shrimp nauplii. Then I'll watch how they grow and feed them live food according to their size. Do not over feed the fry in the beginning. You don't want to polute your tank, remember you don't have a filter in the tank. After the fry reach a size of approx. 1/8 of an inch. I'll install a small sponge filter to the tank.
Good luck to you. Mike