You can clean with bleach and I was told you could also add a very mild bleach solution to your water all the time and it would not hurt your chickens and keep the waterer clean. I will probably go with a apple cider vinegar mix in my water. Sounds more natural and safer than bleach to me. Another person told me not to over think it, they are just chickens and they will drink from mud puddles, or any other water source if they have to.....I feel good stuff in the chickens, good stuff out (eggs)....