Just a few notes about fish safety: Tilapia is cheap because 95% of it is imported from Cihina, where environmental controls are questionable. I haven't eaten tilapia in years. Flounder and salmon cost just a bit more and are healthier. Also, if you're concerned about mercury at all, avoid large predator fish like swordfish, grouper and mackerel. Since they eat smaller fish, the mercury load in their body is larger and thus more likely to cause problems. Here's more info:
The Super Green List from Seafood Watch
Seafood Watch also has downloadable guides for buying safe, sustainable seafood and a mobile app for looking them up when you're in the store.