I put four in my tank and they decimated the snail population. Unfortunately once the snails had run away to hide the barbs ignored the courgette I was feeding them that they happily ate before discovering the escargot! They then bullied each other to death because four is not enough for a peaceful group apparently (5 and up is best), it was either that or the chloramine that must have been added to the water, I live in Edinburgh and this was around the same time the tram works were going on, so inevitable really. I was a water sitter and eschewed using dechlor, until I found out about chloramine. I suppose that could have done the snails in, it was en masse and the graveyard of shells was entirely under the substrate air stone and nowhere else in the tank, but the barbs were smashing their way through the population before they disappeared.
Getting something to scavenge the eggs might work, but I have no clue what would attempt to eat the big bags of jelly.
I have seen my tetras eat the snails that fall from my Frogbit, its a mad dash to get to the snail before its had a chance to go 'oops' and pop itself back into its shell on the free fall.