Neon tetras

Mark,
Hello again. You might be better with (if possible) a three males-to-two females ratio, this might help with the egg predation. Secondly they are best spawned in a darkened-out tank as the eggs are phototropic (I think that's the right word to describe it - light sensitive). This would also help with the egg-eating since many would go unnoticed in almost total darkness.
Are you using a dense amount of plants to catch/hide the eggs? They are slightly adhesive and would catch up in the 'undergrowth'. Java Moss would be excellent for this purpose - and no, a carpet of marbles would be of little or no use as they eggs would be more likely to stick to them than fall through them and I always found marbles to be a bit of a 'turn-off' to the reproductive 'urge' of any Fish I would put into the tank with breeding aspirations.
Although this mightn't be the effect if covered by a dense mop of Moss.
Lastly, the females return to spawning condition pretty rapidly but you would be best served by leaving the female (or more than the one?) in situ for perhaps a week the reintroduce males (but never less than the amount of females, preferably on the 3/2 ratio) after dark then black-out the tank straight after.
The fry are tiny but hatch most times within 24-36 hours and look like slivers of glass everywhere. When you see these remove the parents but do not try to feed the fry until they are free-swimming. Then you will need infusoria to start with and brine shrimp (newly hatched) to back these up once the fry grow large enough to eat them.
Good luck with your venture.
A 'blow-by-blow' account would be nice?
John