Remember also that the source of the shrimp, tilapia, etc. is important.
Shrimp and tilapia farmed in Asia and Central America are frequently farmed in less safe and clean conditions than in the US:
http://www.montereybayaquarium.org/cr/seafoodwatch.aspx
Consumers should "Avoid" imported farmed shrimp unless they can be certain that the shrimp is from farms in Thailand that use fully recirculating systems, which are a "Good Alternative." U.S. shrimp farms are subject to more stringent environmental laws, making these shrimp a "Good Alternative."
In the U.S., most tilapia is farmed in closed inland systems that guard against escapes and pollution.
Matt
http://www.businessweek.com/news/20...-pig-feces-approved-for-u-dot-s-dot-consumers
The problem which I just heard recently on the subject of frozen fish/seafoods is that 90% are imported. Can't go to a local supermarket around here and find good ole US caught or farmed fish. I have checked on US farmed shrimp ordered from southern farms in US but the prices are just rediculous to even consider when you are feeding large predatory fish and rays.