This might be partially my fault because I let it sit for so long, but a few months ago I ordered this product and premixed a gallon of the water/mouthwash mixture so it would be easier to fill the dog bowl when it got low. It ending up being a medical cause that was making my dog's breath bad, so once that was fixed, I stopped using the mouthwash. A few months later,I started giving it to my dogs again when my new dog had bad breath. Well I gave it to them about 4-5 times before I noticed that some kind of algae was floating in the gallon of the mixture. Hopefully it's harmless since my dogs have been drinking the water a couple weeks, but I'd be wary of this product because who knows what's in it if it can form algae in a sealed container.