I'd encourage you to put him on an at least part canned, if not entirely canned diet and mix in extra water for a while. If he does have crystals you want his urine to be very dilute to flush them out, so that he does not block. (and it certainly won't be bad for him even if he just has a UTI). Some of the more holistic foods use the same things that people use for UT problems too - cranberries and blueberries. If you can get him to eat/drink some of that I can't see that it would hurt (both are urine acidifiers) - but the trick might be getting him to actually eat them... My wierdos will eat dried blueberries if I drop them on the floor. You can get a powder acidifier at some pet store too - but I believe it shouldn't be used long term, as it can cause a different kind of crystal.