Hello Feehan and congrats on the new apple snail! I'm new to snails as well. Snails are more active at night. I give my zucchini, a few times a week right after the lights go out and then I remove it in the morning. I wouldn't leave it in there more than 8 hours or so. Zucchini has
calcium which is great for the snail shell. I also added 1 whole egg shell to my tank for calcium as well.
Have fun and enjoy your new snail! I posted a link at the bottom that you may find helpful.
Ken
Apple Snail Care Sheet @ petfish.net