I wonder if pond snails are considered an invasive species. I know hornwort is.
I have been having a little bit of a pond snail issue as well recently. I decided to downsize from 3 tanks to 2, so that meant taking down my 5.5 gallon natural planted tank. So I didn't have to throw away the plants I got a pot and filled it full of the soil and gravel from the old 5.5, planted a ton of wisteria in it, and put it in my 10 gallon. All the fish love it, and I get to keep my plants. Happy ending! Back to the subject of pond snails, when I was doing this I had left some of the soil with a little bit of water in one of my buckets. I was going to clean it out today, and found a little pond snail. 2 days in maybe 50 mL of water! haha The things are crazy hardy. I love the little guys, they add a bit more life to the tank. I would reccomed waiting for your plants to grow a lot, and trim them into smaller pieces to put into the jars. Or get a bundle of hornwort, as it multiplies like rabbits (or pond snails heehee). If I were you I would be doing 2 water changes a week. Have you thought of getting a smal tank, like 1 gallon or so, and putting all of the snails in it? Or even a plastic tub? It would be easy to clean, and you only have to clean one container instead of seven.