Hey there, Melissa. Glad to meet you. Poor snail. It depends on how bad it is. Mostly it is a cosmetic problem at first but the algae can take over. It can be killed by wiping the shell with Hydrogen Peroxide. Rinse with fresh water. Don't get the peroxide on the skin of the snail.

The fry will need some where they can hide. I use a lush underwater hedge of plastic plants. What species are the fry? At that size they sound more like minnows.

Thanks for your response sleepless. It looks like I will be scooping some snails out of the pond today.

We are lucky enough to have a pretty nice aquatic store within a few miles of us. I noticed while shopping for plants and such, when you pulled up a pot there were numerous fish swimming amongst the plants. When I brought them home I found the jelly type stuff on some of the pots. Not knowing what they might be...frogs, fish or something else I might not have picked on my own, I wiped it off before putting in the pond.
With that said, from the pics of minnows I have looked up, they are not the same body shape. One is a longer, thinner body that is orange, white and a little black. The others are brown with a lighter underbelly and have the same body shape of...maybe a blue gill. In others words, I have no idea what they are :) I have pics, but have not figured how to add them to a post yet. Again, thanks for the help!