* Digestion: Your body processes different foods at different rates, but it's not harmful to eat them in different orders. Cereal is generally digested quickly, while fish takes a bit longer.
* Nutritional Concerns: There's no real dietary conflict between cereal and fish. They offer different nutrients and won't negatively interact within your body.
The Bottom Line: It's entirely up to your preference and what you're looking for in your meal. If you enjoy cereal and fish together, go for it!