The Ultimate Guide on How To Tell If Tilapia Is Bad?

Tilapia is a freshwater type of fish. It originated in Africa and now raised in fish farms all over the United States and worldwide. It is a very good source of vitamin and protein such as Omega 3s fatty acids, Omega 6s and Vitamin D.

Tilapia fillets have amazing taste with light flavor that can please even the pickiest diners. It is also affordable and popular, and many people may be confused about not picking the highest quality one. If you are wondering how to tell if tilapia is bad, then this article is for you.

Let’s dive right in!

How To Tell If Tilapia Is Bad?

how to tell if tilapia is bad

Fishy smell

Most freshwater fish have a distinct fishy fish smell.

The seafood smell results from an amino-based substance (NH). Typically, trimethylamine NH (CH3) is the most prominent chemical that creates the smell. It has also been quantified that in 100g of freshwater tilapia will have 66-116 mg of this substance, so the fact that they have a fishy smell is inevitable.

However, when being badly damaged, the raw fish’s smell will be different.

When the tilapia goes bad, the immune system will stop, and bacteria are free to multiply. The abdomen’s fat and intestines are the fastest rot parts and produce a fishy smell.

Some bacteria can turn volatile into trimethylamine and carbon monoxide on fish during decomposition, causing unpleasant odors. 

Sticky appearance

The skin and tilapia meat is covered with mucus, secreted by glandular cells. It is also rich in fluids such as immunoglobulins, hemolysis, and lectin (carbohydrate-based protein with no enzyme activity).

The Tilapia skin acts like immune substances to avoid parasitic animals, bacteria, and small organisms in the invasive water environment. Thus, you can spot a bad tilapia by looking at its flesh.

Once you take the Tilapia skin off, just like how you remove salmon skin, you will see the whole body losing its luster, resulting in a pale color. When you pick the middle of the body up, the fish will bend downwards.

A useful tip to check if tilapia is bad is pressing the center of the body. If the flesh is loose and doesn’t stick to bones, chances are the fish was rotten. Sometimes, the fish meat might be a bit sticky and slimy.

Especially if you let the whole fish spoil for too long, when pressed into the body, it will sink into an inelastic hole with the shape of your finger.

Thick fluid

At this time, you can see that the scales will peel off and have a pale color, sticky, and no longer shining. Some tilapias also have a liquid coating that forms a layer of slime on their body.

Depending on the level of preservation condition, the surface layer will be thick or thin. Mucus is also secreted from gills. The gill lid will open, and secretions of mucus have an unpleasant, viscous-like odor.

Long time refrigerating

Most people think that keeping food in the refrigerator will prevent spoilage. If you are one of them, you are wrong. If you have kept the seafood in the fridge for a few months (6-9 months) or the date has expired, throw it away immediately as it is likely to be spoiled and become bad.

Food storage work on a method that inhibits bacteria’s production and growth level by storing them at low temperatures so that foods stay fresh and do not stink.

However, this method does not guarantee 100% safety for the package foods, and your tilapia can still go bad after a couple of days.

So, how long can tilapia stay frozen?

Studies reported that food should not freeze for more than a month (6-9 months will be too long). In this environment, some bacteria can still grow and cause the decomposition of saturated fat and spoilage.

Besides, refrigerators often contain many microorganisms from other dishes that will enter the tilapia and damage it faster.

Besides, each time you defrost tilapia, the amount of nutrients in it has been reduced a lot. Worse, the freezer may contain viruses that can affect your health, especially the heart. So, freezing is not advisable.

Long time put at room temperature

According to the FDA, bacteria are active strongly at about 4.5 to 60 degrees Celsius. The average room temperature, even with the air conditioning on, will be about 25 degrees Celsius. Eating spoiled fish at room temperature will give you food poisoning and many other health concerns.

At this point, you might be asking yourself how long does tilapia last. The answer is about 90 minutes. They will rapidly decompose, appear foul and become soft.

How To Spot Good Tilapia?

It would be best if you looked at the eyes first. The fresh fish will have sparkling and clear eyes, easy to see the pupils inside. As for badly damaged fish, their eyes are usually opaque and translucent.

For gills, they should have bright color, free of wet and smelly mucus. They should have the characteristic smell of the ocean, not the smell of decomposing.

Another tip is to use your hand to gently press the fish meat, especially the part near the belly; it will be easy to recognize which fish is fresh.

They will have very firm flesh and good elasticity. Meanwhile, the bad one has softer flesh that sometimes becomes limp and has a mucus layer on the surface.

The anus on a fresh Tilapia should also be firm, not ruptured, and have no intestinal waste. If conversely, there will be a lot of fluid because the anus and belly are ruptured.

Therefore, you should remember to be gentle not to damage the fish and accidentally splash yourself when checking.

Last but not least, delicious tilapia usually has a shade of gray characteristic of the species. In particular, the scales have to stay firmly on the skin.

If the above criteria are met, this is a very tasty aquaculture fish, and it will be a perfect alternative for expensive seafoods like haddock fish , Alaskan Pollock or even Pacific Cod.


How long does tilapia last in the freezer?

If kept in a cold storage environment about 3-4 degrees Celsius, raw tilapia will stay at its quality standards for about 1-2 days.

Frozen tilapia with a temperature below 0 degrees C will be good for months or more. Letting it stay in the fridge for longer may cause bad taste.

You should also note that storing in the refrigerator for a long time (approximately 6-9 months) will evaporate vitamins such as omega 3s fatty acids, omega 6s and vitamin D.

Some substances can change and cause severe health concerns such as heart diseases. It will be as harmful as eating bacon.

Can fish go bad in the freezer?

As mentioned above, YES. Refrigerated fish can still be attacked by bacteria that break down the flesh structure, making it go bad quickly.


Tilapia contains a high percentage of protein, omega 3s, omega 6s fatty acids, rich in nutrients that can keep your heart healthy. They also have light flavor and do not have any toxins that can be dangerous to humans.

We hope that our above answer to the common question “How to tell if tilapia is bad?” will be of great help to you about food safety. Thank you for reading.

Kevin Richard

Hi all! I’m Kevin. I spend plenty of time in the kitchen every day because I love cooking healthy and delicious foods for my family and friends. Cooking gives me a chance to be creative and fun. It’s also one of the most meaningful ways to express my love and take care of my little family.

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