In the last 5-10 years, tilapia has taken-over the fish counter at supermarkets for a "mild-tasting white fish" that's economical (sometimes, as cheap as $3 per pound). I've personally been staying away from it recently because I find that it often has a background taste of dirt. It's a personal taste thing. Now, I think I know why.
It's amazing how much you can learn about your food's origin (and slowly become a hippie-foodie in the process) by watching Mike Rowe's Dirty Jobs on the Discovery Channel. While he doesn't intend to be an eco-show, he kind of ends-up exploring the foods we eat anyway. Last night, I saw an episode where he's on a fish farm in the middle of the Mohave desert.
While the farm itself had some great practices such as not releasing their dirty and medication-laden water into the ocean (they process and recycle it), I was shocked to hear about their feeding methods. This particular farm specializes in striped bass (bet you didn't know your bass came from the desert). When they're done with a pool of water, they dump-in carp and tilapia fish. Why? Because, apparently, carp and tilapia will eat other fish's poo.
You heard me right. The tilapia and carp are put into the poo-laden water as the first part of a water treatment process. Once the fish eat up to 30% of the solid matter (both poo and uneaten food) and fatten-up a bit, they're harvested and shipped-off to market with their bass buddies.
I don't think I need to even express how gross this process sounds, even if it's FDA or USDA approved for a fish I'm going to consume.