You are exactly right. Normal fish is good for you because it has Omaga-3, which is good for you. Talapia has Omega-6 . which is terrible for you.
How Tilapia is a More Unhealthy Food Than Bacon
Research has found the inflammatory potential of farmed tilapia to be greater than a burger, doughnuts—even pork bacon! It gets worse.
https://www.health.harvard.edu/newsletter_article/Flap_over_tilapia_sends_the_wrong_message
Omega-3s and omega-6s are both essential fats, meaning they are required for health and development and that the human body can’t make them from scratch but must get them, or their precursors, from food.
The key concern over omega-6 fats revolves around linoleic acid, the main omega-6. It is converted into arachidonic acid, a substance the body uses to make many important molecules, including some that stimulate inflammation and some that fight it, some that promote the blood’s tendency to form clots and others that discourage it.
In theory, eating too much omega-6 fat and too little omega-3 fat could promote inflammation, and thus heart disease. The Wake Forest researchers took this tack. To put their findings in perspective, they wrote, “All other nutritional content aside, the inflammatory potential of hamburger and pork bacon is lower than the average serving of farmed tilapia” because tilapia has more omega-6 fats and fewer omega-3s than red meat.
But the notion that omega-6 fats are bad just hasn’t panned out. For one thing, how the body uses arachidonic acid doesn’t depend on the ratio of omega-3 and omega-6 fats. For another, the argument overlooks the other good things that omega-6 fats do. These include lowering LDL and triglycerides, boosting protective HDL, and helping control blood sugar by making muscle cells respond more readily to insulin.