I have been eating Tilapia pretty much every day for lunch for the past couple of weeks. Do I need to be worried about toxic levels of mercury? Should I switch to a different fish or just eat fish a little less?
If you're worried about mercury then stick to fish that are fresh caught and not farm-raised. Farm-raising fish leads to higher levels of toxic materials for a variety of reasons, and they'll have less of their real nutritional value much the same way that grass-fed beef is healthier than corn-fed beef.
The whole heavy metal poisoning scare with fish is mostly media hype. Creating a huge scare about heavy metal toxicity gets better ratings than saying "Yes farm raised fish does have slightly higher levels of mercury, but you would have to consume aa metric ton of this fish in a week to see any effect." It is not an outright lie the media is reporting, but there is some smudging of the facts.
Eat sardines, wild salmon, chunk tuna. Levels are pretty low. At least I hope so. If not, I have eaten enough that they will have to bury me in a toxic waste dump when I kick.