Why Are My Fish Not Eating? What To Do?

It isn’t a surprise that fish can sometimes stop eating, considering how extremely sensitive they are. These tantrums are actually an indication of some sort of a problem in the fish tank.

There are many possibilities of why your fish has stopped eating. It can be anything from a sick fish to an improper tank setup. Basically, all that you have to do is get to the bottom of the situation to find out the cause in order to solve the issue before your fish starve to death!

Reasons Fish is not Eating (Video)


I’ve listed all the possible causes down below. You’ll also find relevant solutions next to each one. All you have to do is identify the problem and take relevant steps!

Dirty Water

To be honest:

If you ask me, fishes are quite the brats. They will not eat if they find their environment dirty. Of course, the fish poop, pee, and eat in the same water. Unlike their natural habitat, the fish tank needs to be rid of the leftover food along with debris and dirt that gathers over time.

What you can do to prevent the tank from getting too dirty is to regularly change the water. No, you don’t have to replace the entire tank’s water at once, that will kill your fish.


Replace 10% to 15% of the water on a weekly basis. If you have installed a filter, things will be more convenient for you. Remove visible waste that gathers on the bottom of the tank every day. Moreover, invest in a tank water tester to stay aware of the condition of your fish tank at all times. Basically, you have to ensure that the ammonia content doesn’t get too high. Alongside this, the levels of oxygen and nitrogen shouldn’t fall below the optimum levels.

Wrong Water Temperature and pH

Clean water isn’t enough. Yes, fish are very demanding. They are not easy pets. Their environment needs to be perfect for their good health and long lifespan.


Start by figuring out what kind of fish you own. Certain fish breeds are coldwater fish, whereas others prefer warmer water. Coldwater fish are the happiest in the water at around 60 degrees Fahrenheit. Generally, warm water fish, also known as freshwater fish, are happy in water between 74 and 80 degrees Fahrenheit.

If the water gets too cold, the metabolism of the fish slows down. Since fish cannot regulate their body temperature, colder water makes them lazier. This furthers lowers their appetite. Your fish may starve to death if the temperature isn’t brought back to normal quickly.

But what if the water gets too hot?

The fish may not be sluggish anymore, but it isn’t a good sign either. They will get extremely hyperactive and uncomfortable. It will be harder for the fish to absorb oxygen. The stressed situation will keep the fish from eating normally and may lead to death.

As for pH, different breeds have varying requirements. You’ll have to prepare the fish tank water accordingly. To maintain the temperatures, you should use aquarium heaters or fans. Use the right tools to keep an eye on the pH and temperature at all times.

Bad Lighting

The lights inside the aquarium, as well as around the area, need to be monitored. Lighting has two effects. Firstly, it defines the schedule and timing for the fish. Secondly, it plays a role in the development of good bacteria that maintains the optimum chemical balance of the fish tank.

Here’s the deal:

The time when you turn on the lights is when the day starts for the fish. Moreover, turning off the lights communicates night time to the fish. This schedule encourages fish to eat at their defined time. You can establish a routine of mealtimes with the help of your lighting schedule.

This is the reason why it isn’t recommended to keep a fish tank in your bedroom. Allot a separate space for the fish, so that nearby lights don’t affect their routine.


There’s the lifecycle of good bacteria that is being affected by light. It is especially a prevalent factor in reef aquariums. These good bacteria survive on a specific type of light. This light is usually provided by bulbs that are specifically designed for aquariums. You should always check the details of the light you install in the room with your fish tank. Make sure it mentions that it is safe and appropriate for aquariums. It’s important to encourage the survival of these bacteria as they provide certain nutrients to the fish.

Parasites and Infections

While good bacteria is important for healthy fish, there are other micro-organisms that find a home in the fish tank too. These micro-organisms are bad because they cause the fish to lose their appetite along with numerous other issues. It is not unusual for parasites such as leeches to feed on your fish. Things like ich are another common sight in aquariums.

The bad news is:

These parasites are a single-cell organism that cannot be seen with the naked eye. You can only identify these parasites if you see them through a microscope.

What’s even sadder to me is that you can’t spot parasites unless your fish are affected. Infections are a result of parasitical attacks. All that you can do to help is keep a close eye on all your fish at all times. Do a thorough checkup of the fish. Lookout for any visible cuts, scrapes, spots, and other visible symptoms of an infection.

You can also somewhat minimize the risk of parasites by regularly changing your fish tank’s water. Mix in a safe amount of reverse osmosis deionized water as it isn’t a suitable breeding ground for most parasites.


Sickness has the same effect as a parasitical infection in terms of appetite. The difference, however, is that while infection can affect all the fish, sickness is usually targeted towards one fish. Therefore, it can be harder to identify yet easier to treat.


All sick fish show visible symptoms. Protruding eyes, swollen abdomen, upside-down swimming near the surface of the water, hiding behind plants, and loss of appetite are some of the common symptoms of most sicknesses.

If you notice unusual behavior in any of your fish, look deeper into the symptoms to figure out the exact illness. Also, don’t hesitate to take help from a vet in this matter. All animals can get sick, and that’s totally normal, so you don’t have to get worried about it.

Pregnant Fish

Sometimes, pregnant fish give up eating. There can be a couple of reasons behind this.


It is best to give pregnant fish their privacy. They simply do not feel comfortable around other fish in this condition. A small but appropriate breeding tank should fix this issue.

But, this isn’t the only reason why pregnant fish give up food. Live-bearing fish will either stop eating or eat very less right before giving birth. If this is the case, you’ll notice that the swollen belly of the fish has started to get darker. You’ll particularly notice a triangular dark spot near the lower fin.

Wrong Choice of Food

Fishes do not eat food that they don’t like. Monotonous meals will bore them too. A blend of different types of food is not just nutritionally more valuable, but will also keep your fish happier.

You can either mix different types of food for each meal or alternate the choices on a daily basis. Live food, dry food, frozen-dried food, and many other fish food options are available in the market. Also, if you’re feeding commercial food, make sure to double-check the expiry dates before feeding the food to your fish.


Fish do not know when to stop eating. They can very easily overfeed. This may trick you to believe that your fish needs more food than you’re providing. Eventually, you’ll be providing way more than the necessary amount.


A point will come when the fish will be very overfed, and excess food will be left behind. You may perceive that the fish aren’t eating, which is why there’s food settling down in the fish tank. Whereas, in reality, it is the opposite. Your fish are eating fine, but you’re providing more than required. This is causing wastage of food and also an increase in the risk of overfeeding.

What you should do is to research the breed you own. Find out exactly how much food the fish needs at each stage in life. Never offer more food than what’s recommended. Also, most fish only need to be given one meal per day.

Crowded Fish Tank

Remember how I said fishes are total brats. Well, here’s another example that proves it. No matter which fish breed you own, they all hate crowded fish tanks. Even if the breed is a social one, they will hate an over-populated habitat. And what better way to show their disapproval than a hunger strike?

One common rookie mistake is that fish owners will purchase a fish tank according to the size of baby fish. Instead, what you should be doing is to keep in mind the size of each fish when it’s fully grown and mature.

The general rule of thumb is:

If each fully grown fish will be smaller than 1.5 inches, you can keep 7 of them in a 10-gallon fish tank. For fish that are more aggressive in nature, you should go for at least a 20-gallon tank. In the case of bigger fish such as the tiger barbs, a 30-gallon tank is a must. Other than fish, the tank also has to accommodate the decorations, filter, gravel, plants, and other accessories.

Stressed fish

If none of the above seems to be the matter, your fish are probably downright stressed.

In general:

The aforementioned factors are what cause stress for the most part. But, there could be other contributing causes too. For example, your fish may be afraid. Maybe there isn’t enough vegetation for the fish to hide behind when it needs privacy. Also, newer fish tend to take time to adjust to their new surroundings.

Another cause of stress is an imbalance of power among the fish. Certain fish can be dominating, which leads to bullying of the weaker fish. These more powerful fish not only intimidate the weaker fish but also keep them from eating food. The only way to eradicate this issue is to mix breeds in one aquarium after thorough research to ensure that all the breeds will live in harmony.

Related Questions

How long can fish survive without food?

As an aquarist, you should be aware of the fact that fish can survive for two to three days without food. This is important to know so that you don’t leave excess food in the tank when you have to leave the fish behind for a day or two. If you put in two to three days’ worth of food in the tank at once, there is a chance that the fish will overfeed, which is more harmful.

Why is my fish not moving at the bottom of the tank?

You don’t have to panic if your fish is laying at the bottom of the tank. Certain species would do so very often. This is how they like to rest. However, if your fish never did this before and has suddenly started laying down a lot, it is a sign of stress.

How do fishes sleep?

Different fish breeds sleep in different ways. Usually, fish lay down on the bottom of the tank to rest. Some do not lay down but still go deeper into the water. Other fish like to hide behind plants to sleep. Fish like coral reefs continue to swim even while they sleep. Yes, some fish never stop swimming!

Can fish see in the dark?

Naturally, fish are used to dark waters in their natural habitat. Therefore, they can easily move around in the dark. As for vision, they cannot really see clearly in the dark, but their strong senses allow them to be able to feel their surroundings to move around safely.

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