My boy Ming used to get routine blockages until my vet advised me to put him on amitryptiline, one pill per day. This is an anti-anxiety meds that seems to work very well for cats with blockages. Ming kept having repeat blockages until I tried this med (it's very inexpensive, $10 for 100 pills from Pet Meds). As far as diet goes, I feed both my boys Purina One for Urinary Tract Health dry food. Both my cats love this, so I don't have to feed them seperately. I give them a mix of Friskies Special Diet canned food for urinary tract health and Fancy Feast Elegant Medleys. My vet likes both these foods, especially the Elegant Medleys because they have a high liquid content. Ming has not had any problems in over six months (a record!) since I started him on the meds and diet. What's nice is this diet is a healthy one for any cat, so they can all eat the same. Good luck with Gatsby! I used to stress out about this but now I know it can be successfully treated for very little cost or fuss.