Why did my tilapia turned orange?

Chef's answer
The reason for this is due to the frozen tilapia being treated with carbon monoxide (CO). This is usually tilapia that's imported from other countries. It's a way to help the fish look fresh longer by delaying the oxidation of the fish. Carbon monoxide treated tilapia will have a red or orange vein.
Frequently asked Questions 🎓
The best way to tell if your fish is done is by testing it with a fork at an angle, at the thickest point, and twist gently. The fish will flake easily when it's done and it will lose its translucent or raw appearance. A good rule of thumb is to cook the fish to an internal temperature of 140-145 degrees.
Is tilapia safe to eat? When farms rear the tilapia in good conditions, the fish are safe to eat. The U.S. Food and Drug Administration (FDA) list tilapia as one of the best choices for pregnant or breast-feeding women and children over the age of 2 years. This is due to its low mercury and contaminant content..
The best way to tell if your fish is done is by testing it with a fork at an angle, at the thickest point, and twist gently. The fish will flake easily when it's done and it will lose its translucent or raw appearance. A good rule of thumb is to cook the fish to an internal temperature of 140-145 degrees.
Tilapia is a mid-size, flattish fish ranging from about 15 to 30 centimeters in length. ... Tilapia has a soft texture and a mild, minimally fishy flavor. However, like some other types of farmed fish, tilapia is prone to tasting "off"..
The redness is fine, it's the lateral line of the fish. It may taste slightly stronger but there's no need to remove it. ... I personally don't like the taste, but it doesn't mess up the flavor when cooking, and unlike the nasty parts of chicken, it's very identifiable and comes off cleanly after cooking..
Low in Mercury. Because tilapia is a farm-raised fish -- usually in closed-tank systems -- they have less contact with pollution than other fish. This means they have the least mercury possible. Tilapia is so safe, it gets the official thumbs up for children and women who are breastfeeding or pregnant.
That's a filter rated for 100 gallon so it will only just filter 90g... so aquarium stocking levels would apply. You'll probably need two of those once the fish get any real size on. I would say about half a dozen tilapia, but it's a small tank so they wouldn't grow full size.
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