Water It is highly recommended to provide your rats with ONLY bottled water, if at all possible. Tap water, depending on where you live, can contain high levels of chlorinated and/or fluorinated water. Both of these chemicals are toxic to rats. (Be sure the bottled water you choose does not contain either of these toxins as well.) Your rats should ALWAYS have water provided. Water bottles are the best choice in providing water for your rats. Bottles keep the water clean and contained. Although rats prefer water dishes, dishes quickly become filthy and are easily tipped over. Avoid water bottles that make it difficult to see how much water they contain. An 8oz sized bottle is a good size for two rats. You should empty, clean, and refill your water bottle every time you clean your rats' cage. Don't forget to refill their water bottle in between cleanings when needed as well. Be sure to test your newly cleaned/filled water bottle by tapping the nozzle with your finger to make sure it is working properly and that water comes out as it should. In fact you should test your rats' water bottle like this everyday to make sure it is still providing water. A rat can die of thirst with a full water bottle hanging in there enclosure if for some reason the spout is not working. Make sure your rats' water bottle is hanging at the proper height so that your rats can comfortably reach and drink from the nozzle. We recommend using a black marker (if your bottle is glass, be sure to get a marker that writes on glass) and a ruler, to mark out every quarter inch, starting at the top of your bottle (the opposite end from the nozzle), and working your way down the entire length of the bottle to the bottom. This way, you can use these marks to measure exactly how much water your rats are drinking each day, and thusly you will know if they start drinking less or more water than usual. (This can be a sign of illness.) Here, Tabu drinks out of a water bottle. Notice the measurements marked on the bottle. Never add vitamins or medicine to your rats' water bottle. Doing so could cause your rats to stop drinking their water or greatly decrease the amount of water they are drinking. Vitamins in the water should not be necessary if you are feeding your rats a proper diet. And giving your rats their medicine by putting it in their water is a very ineffective way to give your rats medication. There is no way of knowing that each rat is getting a proper dose.