a fish called tilapia

Alberto says: Tilapia is the fifth most important fish in fish farming, with production reaching 1,505,804 metric tons in 2000.

Because of their large size, rapid growth, and palatability, tilapiine cichlids are the focus of major farming efforts, specifically various species of Oreochromis, Sarotherodon, and Tilapia, collectively known colloquially as tilapias.

Like other large fish, they are a good source of protein and popular among artisanal and commercial fisheries.

Most such fisheries were originally found in the Philippines, but outdoor fish farms in tropical countries such as Papua New Guinea, Africa, and Indonesia are underway in freshwater lakes.

In temperate zone localities, tilapiine farming operations require energy to warm the water to tropical temperatures. One method uses waste heat from factories and power stations.

Tilapia have very low levels of mercury  as they are fast-growing and short-lived with a primarily vegetarian diet, and thus do not accumulate mercury found in prey.

Tilapia is a low saturated fat, low calorie, low carbohydrate and low sodium protein source. It is a source of phosphorus, niacin, selenium, vitamin B12 and potassium.
However, farm raised tilapia (the least expensive and most popular) has a high fat content (though low in saturated fats).

According to research published in July 2008, farm raised tilapia may be worse for the heart than eating bacon or a hamburger.

The research suggests the nutritional value of farm raised tilapia may be compromised by the amount of corn included in the feed. The corn contains short chain omega-6s that contribute to the buildup of these materials in the fish. "Ratios of long-chain omega-6 to long-chain omega-3, AA to EPA respectively, in tilapia averaged about 11:1, compared to much less than 1:1 (indicating more EPA than AA) in both salmon and trout."

Wide spread publicity encouraging people to eat more fish has seen tilapia being purchased by those with lower incomes who are trying to eat a well balanced diet. The lower amounts of omega-3 and the higher ratios of omega-6 compounds in US farmed tilapia raise questions of the health benefits of consuming this fish.

Adequate diets for salmon and other carnivorous fish can alternatively be formulated from protein sources such as soy, although soy-based diets may also change in the balance between omega-6 and omega-3 fatty acids.