100% natural solution to the burn marks that appear on grass after your dog urinates on the grass. How? You simply place the rocks in your pet's drinking water and they work like a sponge and absorb excess nitrates and other trace elements from your dog's water. This means there is less of a concentration of nitrate in your pet's urine which ultimately means that the pee will not kill your grass. Less nitrates in, less nitrates out! 200g.