You have to be careful with tuna...there are a lot of things in it that can be detremental to your cat's health.
http://www.maxshouse.com/Tuna_and_Ca...onal_Facts.htm

I've read a lot of stuff on Iams. If you don't like that company, be mindful of the other products they sell...like, Eukanuba.

We feed Royal Canin and are very happy with the results.