We've always been told that fish is a great way to boost our brain power and keep our minds sharp. But all that fish comes with a risk. Depending on the type you eat, you could be getting a dose of mercury with every bite. The scariest part is that you may have no idea. While symptoms like fatigue, irritability and tremor can show up with higher levels of mercury, lower levels may go completely unnoticed. Getting your blood level checked if you eat a lot of fish is a good way to know if you've been exposed, but you can also try avoiding fish high in mercury. To find out which fish are safest when it comes to mercury, check out our low-mercury fish guide.