Well, I don't know other than taking them out of the dirt and rinsing them well with dechlorinated water. Just to let you know though, peace lillies aren't aquatic plants, so if you submerse them, they will die after a while. Oh, and the apple snail you have will get to be 5-6" big, and makes a lOT of waste... you may want to consider moving it somewhere else and getting a smaller snail... maybe a mystery snail. I had a few and found out they were causing some problems bc of the large amount of waste they make. I had to exchange mine for a mystery snail, too.
Don't you just love the ADFs and cories! They are so cute!
Good luck!
