Are Cardinal Tetras Prone To Obesity?

Cardinal tetras are small, colorful freshwater fish that are popular for aquariums. Usually, these fish are active, and it is interesting to watch them swim around the tank. Thus, after a hectic day, most owners prefer to feed their fishes and watch them. Unfortunately, while fascinating upon their movement, some aquarists fail to realize that cardinal tetras, like other fish, are prone to obesity.

Cardinal tetras are indeed prone to obesity. They are omnivores that can eat both plant and animal matter. They are very fond of eating. So, Cardinal tetras tend to consume more than what is necessary, which results in obesity. It may be due to a lack of enough exercise or excess consumption of high-calorie food.

Though keeping fish are a lot easier than other pet. But, there certainly are some responsibilities that you need to fulfill. In this blog post, we are going to explore the feeding responsibility of the Cardinal tetras owner. Are you ready?

What Do Cardinal Tetras Eat?

Cardinal Tetras are omnivores. They eat a variety of plants and animals. They eat various insects, worms, crustaceans, and plant matter such as seeds or leaves in the wild.

But in an aquarium, Cardinal tetras will eat a wide variety of food. They are not picky, and you can feed them both meat-based foods such as shrimp pellets or algae wafers and plant-based foods like flakes or brine shrimp.

However, most Cardinal tetras enjoy eating freeze-dried bloodworms. You can also feed them live insects such as brine shrimp, daphnia, or bloodworms. These will make your Cardinal Tetras very happy.

Are Cardinal Tetras Prone To Obesity?

Cardinal tetras are usually an example of a fish that loves to eat. And yes,  it is true they do enjoy their food. However, obesity in cardinal tetras is not the same thing as human obesity.

Most fish do not have a way to accumulate large amounts of fat in their bodies. When fish experience weight gain, it is due to overeating and lack of exercise instead of an accumulation of fatty tissue.

Because cardinal tetras love to eat, overfeeding them can lead to obesity. Besides this, fluctuation in the water conditions, inbreeding, and other illnesses can also contribute to obesity in Cardinal tetras.

Signs Of Obesity In Cardinal Tetras:

Due to the lack of proper feeding information, obesity is a growing issue in the aquarium hobby. A cardinal tetra can become obese if you fail to keep them within its ideal weight range.

Usually, this can cause serious health problems down the road. So being aware of these signs and symptoms of obesity will help you get your fish back on track. Moreover, the symptoms of obesity in cardinal tetras are not challenging to spot.

One of the first signs of obesity is a swollen belly. It happens because the fish eats more food than its body can handle. Thus, their body stores the food as fat instead of using or expelling it. The other symptoms that can let you know that your cardinal tetras are obese include:

  • A sluggish response to its environment.
  • Increase in the time to swim back up after being at the bottom of an aquarium.
  • Lethargy and lack of interest in playing or mating with other tank mates.
  • Increased respiration due to the strain of carrying all that extra weight.

If you spot any of these symptoms in your cardinal tetras, it is time for a diet.

What Are The Causes Of Obesity In Cardinal Tetras?

Cardinal Tetras are not naturally obese, but they can become so if they have unbalanced or contains too much food. Apart from this, a few other reasons contribute to obesity in Cardinal Tetras.


Feeding your Cardinal Tetra too much food is the most common reason why you will find them overweight. To keep a check on their weight, you must provide only as many flakes or pellets as they can eat within two minutes and remove any excess from the tank immediately.

Inadequate Exercise:

In the absence of enough space to move around and exercise, Cardinal tetras tend to gain weight. Therefore, you must provide your fish with a big tank or some other large water body where they can swim about as much as they like without bumping into anything else.

Fluctuation In Water Condition:

If there is a sudden change in the water conditions of your tank, it will affect the health and well-being of all inhabitants present inside. Usually, Cardinal tetras tend to eat more in such situations. Usually, this is because their digestive system becomes disturbed, and they want to compensate for this by eating more food.

Inadequate Tank Size:

If your fish tank is not of appropriate size, it can cause obesity in Cardinal Tetras. They require a lot of space to swim around and play, so make sure that you provide them with enough room for this. In addition, an overcrowded aquarium will lead to stress among the fishes, which can eventually result in obesity.

Inadequate Lighting:

Cardinal Tetras are a schooling species and love to swim around during the daytime when there is ample light in their surroundings. Keeping your tank under insufficient lighting will affect them adversely as they won’t exercise properly. Not being able to exercise appropriately will cause obesity.

Cardinal Tetra Diseases:

A few diseases can lead to obesity in Cardinal Tetras, such as Swim Bladder Disease and Dropsy. Therefore, it’s necessary to take good care of your fish and provide them with the appropriate environment so that they don’t contract any disease or disorder that may result in their obesity.

Wrong Nutrition:

Cardinal Tetras require good quality of food since it is a significant factor in their lives. If you feed them low-quality food, they will not get the proper nutrition, leading to obesity over time. You must avoid feeding your Cardinal Tetras fatty or deep-fried foods since this makes them obese pretty quickly.

Signs That You Are Overfeeding Your Cardinal Tetras:

Sometimes you fail to realize that your cardinal tetras are overweight and you are overfeeding them. It is essential to keep in mind that you are dealing with fish here, and they can become obese, which impacts their health.

  • However, some of the signs that you are overfeeding your cardinal tetras are:
  • The cardinal tetras stick to the surface of the water.
  • They have a distended stomach which is full of food that they cannot digest. So, this leads to indigestion and constipation.
  • There will be more uneaten food at the bottom of your tank than there would usually be if you were not overfeeding them.
  • The cardinal tetras feel irritated and start fin nipping each other. It is a sign that they feel stressed out because of the amount of food in their diet.
  • The presence of algae in your tank the reason for this is that there will be more uneaten food at the bottom of your aquarium, which becomes food for algae.
  • Cardinal tetras tank appears dirty and smells bad even after you have done your weekly water change.

Some Tips To Manage The Weight Of Cardinal Tetras:

The average size of an adult Cardinal Tetra is about 0.75-2 inches in length, but some specimens can grow to a weight of around one ounce. Therefore, if you have a school of Cardinal tetras in your tank, they may start gaining more weight over time which is not normal or healthy.

If you want to avoid obesity in the fish that you have at home, there are a few tips that you can follow.

The first thing to do is feed your Cardinal tetras small portions of food instead of large ones. Then, the best thing to do is make a timetable for the amount of food you will be feeding them.

Similarly, emphasizing quality rather than quantity is another way to ensure that your Cardinal tetras are not obese. It means focusing on the type of food you’re giving them.

Another tip for avoiding obesity is by performing regular tank cleanups. A clean environment will allow proper digestion because it reduces the amount of waste that can lead to quick weight gain.

In addition, maintain an ideal water condition inside the tank at all times since this may cause stress for your fish, and they will store food as a defense mechanism.

Finally, you need to pay close attention to how much you are feeding them compared with their actual consumption.

How Should You Feed Your Cardinal Tetras To Avoid Obesity?

Cardinal Tetras are beautiful, peaceful fish that makes an excellent addition to the community tank. However, there is one potential problem with these bit of swimmers – they can quickly become obese.

This obesity may seem harmless during their younger days, but it will get worse as your tetra’s age and eventually affect their health negatively. To avoid this in your aquarium, make sure to feed in moderation and avoid keeping them in a tank with less than half of their body length.

What Should You Feed?

Cardinal Tetras eat various foods, including flakes, brine shrimp, bloodworms, and even daphnia. Just make sure that the food you’re feeding contains at least 40% protein content each time to avoid obesity.

How Much To Feed?

Most experts recommend feeding your tetras twice a day. However, it is best to wait for about five minutes after you feed your Cardinal tetras. Then, remove all the uneaten foods from the tank. It will prevent your fish from overeating.

How Often Should You Feed?

Since this fish species can live in community tanks, make sure not to overfeed them by only feeding once every two days if necessary. It is best to feed them in the morning and at night to allow them time to digest before sleeping.

What About Treats?

Cardinal Tetras love bloodworms, brine shrimp, and tubifex worms as their treats but make sure that it’s not more than once or twice a week. You can also feed your tetra pellets, but these mostly contain carbohydrates and protein that can cause obesity if given in excess.

Bloating Or Obesity In Cardinal Tetras?

Most of the time, aquarists fail to distinguish between bloating and obesity. Bloating can result due to many reasons. Usually, it is the result of constipation or swallowing air at feeding time. On the other hand, obesity in aquarium fish comes from overfeeding and often lack of exercise that causes their bodies to fill up with excess fat tissue.

Some of the signs that indicate your Cardinal tetra is bloating are:

  • Distended stomach
  • Inability to swim properly
  • Loss of coloration and appetite

If you notice any of these signs, you may help your fish by changing the water, giving it an easy-to-digest food, and doing a partial water change.

Pregnancy Or Obesity In Cardinal Tetras?

Since Cardinal tetras live more happily in groups, most owners prefer schooling them. Moreover, while keeping them in schooling, pregnancy is not unusual as they breed quickly. Thus, it is essential to keep an eye on the fish for any changes in behavior.

If you notice your cardinal tetras becoming obese, it could be due to pregnancy or obesity. Some of the signs that will help you to know your fish is pregnant and not obese are:

  • Pregnant cardinal tetras are active and appear healthy, whereas obese fish are inactive and show poor health.
  • Pregnant cardinal tetras have a full stomach. But obese fish has a distended abdomen filled with air.
  • Pregnant cardinal tetras are more colorful than obese ones.
  • Pregnant cardinal tetras have a black spot near the dorsal fin, which is absent in obese fish.
  • Usually, pregnant cardinal tetras tend to hide in a safe place. They do not like to be near other cardinal tetras or at the center of a group, whereas obese fish love being in spots where they can easily see their surroundings and are very active.

If you notice some changes in your Cardinal tetra’s behavior, it is best to consult with your vet. The reason behind the behavior could be obesity if there are no other signs of pregnancy present in your fish.


Overall, due to the lack of sufficient research on this topic, most aquarists end up feeding their fish a primarily plant-based diet. However, it is not necessarily bad, as most aquarium plants are incredibly nutritious and provide your fish with all the nutrients they need to thrive.

However, suppose you would like to feed your Cardinal Tetras meat or other animal products. In that case, I recommend doing some further research on this topic before making any changes to their diet.

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