Underfeeding Cardinal Tetras | What Happens If You Underfeed Them?

Despite the ease of caring for Cardinal tetras, fish-keeping can be quite tricky sometimes. If you are new to fish keeping, feeding them the right kind of food in the right amount can be a serious problem. So, most beginners often make the mistake of overfeeding and underfeeding cardinal tetras. But have you ever thought about what happens if you underfeed them? What happens if you underfeed cardinal tetras?

Underfeeding your Cardinal tetras can lead to health problems such as swim bladder disorder, malnutrition, and even death. Besides this, when you underfeed them, they feel stressed and become weak. And this makes them more vulnerable to diseases. So you must know the right quantity of food your fish should eat each day before feeding them.

This article is for beginner aquarists who are facing feeding problems. Here, we will be discussing everything about what happens when you underfeed your Cardinal tetras.

What Happens If You Underfeed Your Cardinal Tetras?

Like overfeeding, underfeeding can also cause problems in the aquarium. If you underfeed, then your cardinal tetras will not be getting all of their required nutrients, leading to several issues that may kill them.

Some of the issues related to underfeeding your Cardinal tetras are:


If you underfeed your Cardinal tetras, they will not get the vitamins and minerals that their bodies need to function properly. It can lead them to become weak and lethargic. Thus, this means it will be harder for them to avoid predators or escape from an attack.


If you underfeed your cardinal tetras, they may become so weak that they cannot defend themselves against other fish in the aquarium. In addition, this will lead your cardinal tetras to hide all of the time instead of being active and social with their tankmates, which can cause them a lot of stress.

Neurological Issues

If you underfeed Cardinal Tetras, it could develop neurological issues such as head and lateral line disease, common in aquarium fish. What this will do for your cardinal tetras is cause them to go off their food or forget how to eat properly, both of which can lead to them not eating enough and starving themselves.

Swim Bladder Disease

If you underfeed your cardinal tetras, they may develop swim bladder disease, one of the most common diseases in fish. Swim bladder disorder occurs when a fish’s digestive system becomes disordered, and food gets stuck or moves to either side of its body. It can cause them to appear bloated on one side, affecting their ability to swim properly.

Loss Of Coloration

When you underfeed your cardinal tetras, they will not gain the nutrients necessary to produce their bright and vibrant colors. Unfortunately, this means that they look dull and lackluster compared to other fish in their aquarium, which can cause a lot of stress.

Lack of Energy

When you underfeed your cardinal tetras, they have a lack of energy. Thus, this can lead to them being unable to seek out food in the aquarium. What this will do for your Cardinal Tetras is cause them not to eat enough or fast too much, both of which can be deadly.


Underfeeding Cardinal Tetra could lead to death as they will not get their bodies’ nutrients to survive. It will lead them to go into a state of starvation, which can cause serious health problems, and if left untreated, it could result in death.

How To Feed Your Cardinal Tetras?

Feeding cardinal tetras are very easy but tricky. Since Cardinal tetras are omnivores, you can feed them both meaty foods and algae. They usually eat small insects, worms, flakes, or pellets, which are rich in proteins. You should also provide your fish with some vegetables like cucumber so they will have a balanced diet.

What To Feed Your Cardinal Tetras?

Cardinal tetras prefer both animal and plant-based foods. You can feed them small insects, worms, flakes, or pellets that are rich in proteins. They also eat vegetables like cucumber so they will have a balanced diet.

How Often Do I Feed My Cardinal Tetras?

You should feed Cardinal tetras twice to three times daily. But it depends on the species of fish and their size.

How Much Should I Feed My Cardinal Tetras?

Cardinal tetras should be fed as much as they can eat within a minute or two, but don’t overfeed them because this will pollute the water and make it toxic for your fish. Also, remember that feeding cardinal tetra too often is not good either. Since their stomach is tiny, they are prone to bloating.

When Should You Feed Your Cardinal Tetras?

Cardinal tetras are not nocturnal so feeding them at night is useless. Instead, it would be best if you fed your fish early in the morning or during daytime hours when they can see their prey clearly and eat well.

What Are The Best Food To Include In Cardinal Tetras’ Diet?

Cardinal tetras mainly feed on live food. However, you can also give them mosquito larvae, brine shrimp, and other small insects if you do not have a place to go fishing for bait or the time to catch smaller fish in your aquarium.

Besides this, some other foods that will help Cardinal tetras to live longer and healthier are:

  • Algae pellets
  • Shrimp sinking wafers
  • Rotifers and Artemia nauplii
  • Daphnia

If you want to avoid the hassle of catching live food for your Cardinal tetras, we recommend using Hikari tropical fish pellets. They are highly nutritious and do not pollute the water as much as fresh or frozen foods do. The downside is that they cost more than other types of food available on the market.

What About Determining The Right Amount Of Food To Give?

As far as the right amount of food to give is concerned, it depends on several factors. For example, the size of your aquarium and how many fish you have in there determined if they will eat all of what you put inside at once or not. Also, keep in mind that you need to give them more food if they are growing. If your fish do not eat all the food in a couple of hours, take it out and clean the aquarium or put some other type of live food for them.


Overall, one major downside of underfeeding Cardinal tetras is that they will not grow and develop quickly. Another common sign of underfeeding is weakening their immune system, leading to fatty liver disease if left untreated for too long.

Remember that these fish are susceptible to different medications used to treat aquariums. So, sick or diseased fish are quite common. Hence, it is best to be careful with what you use in your aquarium.

If you have any questions or concerns, feel free to leave a comment down below! We would love to help you out! 🙂

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