What is the best dog food for a Bichon/Toy poodle that has crystals or bladder stones?

My 9 year old Bichon has been eating Medical preventive since a puppy (to prevent urinary crystals that are prevelent in this breed) and my 5 year old Bichon / Toy Poodle mix has been eating the same since a puppy but recently had surgery to remove a bladder stone. The vet recommended she now eat Medical SO to prevent further stones. Is there any better, more natural food out there that would be healthier for both of them?|||Medical is very good for your pets! it is very limited in chemicals, and additives. You can only get medical through you vets office and that is because it has medicinal ingredients that store bought brands can't. if price isn't an issue stay with the medical, it is the best for there health, and it is the best brand to further prevent crystals, and bladder stones.|||Increase magnesium in its diet. This will help leach calcium out of its cells and system. It will not leach it out of bone or teeth. It will make them stronger.