We just lost a pony to stones. Two years ago, we removed a huge one from his stall mate. We've had them for about 5 years, (they are both @30). One vet said that the cause is feeding them SoCal Alfalfa. Another said it's the hard water. A stable owner said to put vinegar in the feed. A vet said that does nothing, it would take so much vinegar to make a difference that it would pickle the pony. What is the best way to prevent stones from forming and to slow their growth? We feed hay and pellets. Is there an ingedient in some pellets we should avoid? Is there a water treatment or filtration system that helps?