i am not sure that you can always see if the snail is carrying eggs. I normally gauge by their behavior. Mine will normally start travelling above the water line, completely out of the water. They also seem to be more active right before they lay.
Well, at the risk of sounding crazy-hehe-
I have a gold mystery snail that arrived in the mail yesterday- and it looks like I can see eggs right through her shell- right where the middle of the swirl is-
is that possible? they are tiny and slightly pinkish looking---
I think so, when my magenta died I could see something similar in the "deepest" part of the whorl of the shell. I believe she died from being eggbound.