I have tried with 1 part bleach to 10 parts water. You can dip for 2-5 min and then rinse under running water. Some people do this; some people don't. It all depends on how careful you want to be. Nowadays, I couldn't care for one more snail or two mre duckweeds so I don't really bother. I do, however, let the new plants stay in a bucket full of fresh water for at least 2 hours before I plant them.