Hi and welcome to the forum
Mystery snails are either male or female and need a partner to breed. They can carry eggs for a few days but if your snail has been alone for a year, the other snails are probably new introductions that came in on plants.
Have you bought any new plants or driftwood that was in a tank recently?
Can you post a picture of the new baby snails?
Snails don't normally eat their own kind.
Some fish will eat small snails. Mollies, glass catfish and tetras aren't renown for eating snails.
Without knowing the species of snails, leave them where they are until we identify them. If they turn out to be baby mystery snails, then keep them and grow them up. When they are 1/2 to 1 inch in diameter, sell them to a pet shop. If they turn out to be a pest snail, then squish them.
----------------
What are the tank dimensions (length x width x height)?
What is the GH (general hardness), KH (carbonate hardness) and pH of your water supply?
This information can usually be obtained from your water supply company's website or by telephoning them. If they can't help you, take a glass full of tap water to the local pet shop and get them to test it for you. Write the results down (in numbers) when they do the tests. And ask them what the results are in (eg: ppm, dGH, or something else).
Depending on what the GH of your water is, will determine what fish you should keep.
Angelfish, discus, most tetras, most barbs, Bettas, gouramis, rasbora, Corydoras and small species of suckermouth catfish all occur in soft water (GH below 150ppm) and a pH below 7.0.
Livebearers (guppies, platies, swordtails, mollies), rainbowfish and goldfish occur in medium hard water with a GH around 200-250ppm and a pH above 7.0.
If you have very hard water (GH above 300ppm) then look at African Rift Lake cichlids, or use distilled or reverse osmosis water to reduce the GH and keep fishes from softer water.
---------
Glass catfish need to be kept in groups of at least 6 (preferably 10) or more.
What species of tetra do you have (post a picture if you can't ID them)?
Most tetras need to be kept in groups of at least 10 or more. Some tetras are fin nippers and will cause problems to the mollies and glass catfish.
Mollies need hard water (GH around 250ppm+) and a pH above 7.0. If they are kept in soft water they die prematurely.
Balloon mollies are man made mutants whose bodies have been shortened but their internal organs are still the same size. This causes them to appear short, round and fat. These fish do not normally live as long as their wild counterparts and often suffer from intestinal problems due to having their intestine and organs squished up. I do not recommend people buy any type of balloon fish for this reason.
