Hi, I have a 2.5 gallon mini-aquarium that houses 1 male betta and 2 snails. Decent filtration system that leaves enough algae for the snails, 50% water change weekly.
One snail is a black mystery snail and the other is an ivory apple snail (this is what they were sold as).

I came into my room an hour or two earlier to find a strange, clear jelly-like mass on one of my artificial plants with a small orangish-pink center, the same color as the body of my ivory snail. From what I've seen it looks like an egg to me, but do snails lay just one egg at a time? At first I thought Punch (betta) might have eaten them, but he was as hungry as ever and the egg(?) wasn't there at lunchtime when I went in to feed my hermit crabs.

If this IS an egg, should I separate it from the betta (I have a sliding partition I can use)? Or is it an egg at all? Help! :blink:

The black "mystery" snail is also an apple snails. Both your apple snails, if female, would lay their eggs out of the water. In an aquarium, that would be normally on the glass lid. If the water level is so high that they can't get up there, then they might lay in the water (such eggs would not be viable). I wouldn't imagine that they would lay a single egg but I guess it is possible. Depending on species, apple snails eggs are yellow or pink. Apple snails grow large and will not be mature enough to lay eggs until the size of ping ping balls at least. For more info on apple snails, see applesnail.net which should answer your questions in detail.