With so many cat people on my f'list, I'm not sure if your cats are the ones with bladder issues. IF so, I read an article from a "ask the vet" column yesterday. He said force 1/4 cup of liguid (can be water, chicken broth, anything they'll drink) everyday. One guy wrote in saying his cat had crystal problems with his cat almost monthly until he took a syringe and forced the liquid every night. Says it's been 8 years since the cat has had crystals and the cat is now 15. Also said at first the cat hated it, but now it's not a big deal. Just a thought.