We all that know that we need to provide fresh water daily for our pets, but just topping the bowl off can encourage bacteria to grow. If you feel a slimy residue in the bottom and sides of the bowl, that’s dangerous fungus and bacteria starting to grow. Animals can smell that bacteria and often won’t drink as much as they should, potentially causing dehydration. If they do drink contaminated water, they can become ill.
It is best to clean the water dishes daily. If you have a dishwasher, that is an easy way to disinfect pet bowls. For hand washing, scrub with dish detergent and hot water. A natural alternative is to use equal parts baking soda, warm water and salt.
Plastic dishes are not recommended as they can absorb odors and become scratched, which will make them difficult to disinfect. A better choice is stainless steel or ceramic. Glass is also fine to use.
Now that your bowls are all clean and shiny, consider filling them with spring water or filtered water. Your pets will thank you!
Simpson, L  Invisible Monsters In Your Pet Bowls