We have an 18 month old Doberman and were loosing the battle to keep a nice lawn! I was recommended the dog rocks but figured they would probably be a gimmick but was willing to try - and I'm very glad I did!! I'm only on the first pack which lasts about 2 months but we noticed a difference within the first 3 weeks! I'm now about to buy a second pack and my lawn is looking brilliant - green everywhere and even my rose bush (he decided to make that particular bush a very nice P - spot) has begun to revive itself! I would definitely say its worth trying these if you want to keep a dog and a green lawn!