Is it a headache to you that your perfect grass becomes no more imperfect because your dog urinates on it? With this safe anti-urine stains rocks from Dog Rocks, you won\'t have to worry about it anymore. You just need to place one pack of rocks into a water bowl of about 2 L and these rocks will absorb the excess nitrates as well as other trace elements from the water before the dog drinks it. And less nitrates in, less nitrates out! So less nitrates in your dog\'s urine which ultimately means that their pee will not kill your grass. The rocks will last for two months and will be less effective after this period, so you should change the stones every two months to ensure their effect. Most importantly, this anti-urine stains rocks does not change the pH balance of the urine and has no side effects to your four-legged friends and is even safe for your cat!