Hi Liz,
Thanks for your reply. They're separated because the vet I saw couldn't tell whether he had something contagious. I suspect that he does, since a couple of the others had similar symptoms but nothing as serious or as long lasting. Unfortunately, I've only just been allowed to give him water and I'm supposed to restrict food until tomorrow (should have mentioned this, sorry!), so I can't put it in anything. I'll certainly try with the food tomorrow, but I have a few doses to give before then.