Why is fish-based cat food (wet) bad?

I have read this several times on this site. My cat prefers fish based wet food (scarfs it down); while he will eat chicken and beef based foods -- he will eat much less of it and it takes him longer too (he obviously prefers the fish).

He does eat a chicken based dry food (Nutro) so what should I do? Eliminate the fish based wet food and offer only chicken and beef even though he does not love it as much? Right now I am mixing Nutro wet with Fancy Feast wet (fish based) to get him to eat it. BTW: some of that FF fish food is discusting looking -- makes me want to puke that he eats it.

Another thing is he will only eat loaf or flaked food -- no morsals with gravy.

Here's a link to a previous disscusion about this:

http://www.thecatsite.com/forums/sho...highlight=fish

If you do a search for "fish" or "crystals" you will probably find lots of info .

In addition to possibly having a connection with crystals in certain cats, some cats develop a sensitivity to fishy foods, especially if fed them every day. I was feeding Odo Trader Joe's foods (all of which have fish) regularly, but after several weeks, he began throwing up the food a couple of times per week. I don't think that feeding fish foods some of the time is necessarily bad--it all depends on your cat's level of sensitivity to the food.