I used to feed Storm Royal Canin Urinary S/O because he liked the taste of it better than the Hills C/D. I also liked the fact that it would help prevent both the struvite and the calicium oxalate crystals although I think that the canned version helps with the calcium oxalate crystals better than just the dry. I think that you also need to make sure that Logan gets plenty of water or canned food mixed with water each day. This seems to be the key in preventing UTI's or crystals.

I now feed Storm Innova Evo because Starr and Pearl need to be on a grain free diet. I was afraid to feed this to Storm at first but both my regular vet and my holistic vet said that as long he got plenty of canned food mixed with water every day that he should be okay. He's now been on this food for about 2 years or so and he's doing great. Good luck.