10 Reasons Why Your Fish Is Not Eating

  • By: Kind Of Pets
  • Time to read: 10 min.

Fish is not eating? Fish can be a great addition to any home aquarium, but they will only stay healthy and happy if their needs are met. One of the most important things that your fish need is food!

We all know what happens when humans go without eating for too long: we get hungry and irritable. But how do you know if your fish is hungry?

Most people who keep fish as pets are familiar with the common problem of their fish refusing to eat.

The good news is this article will explore some possible reasons why your fish is not eating and offer tips on how to get them back to eating normally.

So below are 10 reasons why your fish may not be eating, along with solutions on how to fix it!

Fish Not Eating? Here’s 10 Reasons Why!

1. Incorrect Water Temperature

If the temperature of the water is too cold or too hot, your fish will instinctively go into survival mode. This is especially dangerous for tropical fish.

A sudden change in temperature can cause stress on your fish and eventually lead them to stop eating altogether! This can happen more often than not when people switch tanks or water pumps.

Changes In Water Temperature Can Be Because Of The Following:

  • Faulty Water Pump
  • Cleaning Filter May Need Replacing
  • The Tank Is In Direct Sunlight


If the water temperature is the issue, you can try to adjust it by adding or subtracting heaters or cooling units. If it is too cold, add a heater; if it is too hot, remove a heater.

Top Tip: The average water temperature for aquarium fish should be 18°-22°C (65°-72°F). However, if you require a second apinon we do reccomended that you contact your local fish veterinary.

Another solution would be to get an aquarium thermometer to make sure that the temperature is at a comfortable level for your fish.

You should also avoid putting your tank in direct sunlight as this will cause rapid changes in temperature.

Make sure that your filter is working properly and replace it if necessary. Also, check any tubing leading into and out of the tank for leaks.

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2. Feeding The Wrong Type Of Food

When it comes to feeding fish, many pet owners mistakenly believe that any type of food is okay to give them. This, unfortunately, is not the case, as there are certain types of food that can be harmful – or even fatal – to fish.

Fish are also fussy eaters and will only eat food they like. If your fish is not eating, it may be because you are feeding it the wrong type of food.


There are many different types of fish food on the market, so take your time to find one for the type of fish you have.

If you not already doing so… try feeding them live food. This can be a little more work, but it can be worth it if your fish start eating again.

Make sure you are only giving your fish food that is meant for their species! Some pet stores sell universal fish food that is okay for most types of fish, but there are also specific foods made for each type of fish.

Feed your fish a variety of food that is made specifically for fish, such as flakes, pellets, or freeze-dried bloodworms. You can also try live food like brine shrimp or Daphnia.

3 Fish Is Overfed

It is very easy to overfeed your fish, especially if you are new to keeping them. When fish are overfed, they will not eat as much because their stomachs are full. This can eventually lead to them not eating at all.

Overfeeding your fish can not only lead to health problems such as “fatty liver” but can also create an unhealthy environment in your tank. 

Overfeeding Your Fish Can Cause:

  • Fatty Liver
  • Algae Bloom
  • Cloudy Water
  • Clog Your Filter
  • Improper Digestion


If you think you may be overfeeding your fish, try cutting back on the amount of food you are giving them. You should also only feed them what they can consume in a few minutes – any leftover food will only decay and pollute the water.

4. Sudden Change Of Environment

Fish are reactive to their environment and if something in their environment changes, they may stop eating. When you change your fish’s home or introduce them to a new pet, their eating habits can change as well.

A sudden change in environment – such as moving to a new house or changing the tank’s décor or the tank itself – can also cause your fish to stop eating.


If you have recently moved, give your fish some time to adjust to their new home before trying to feed them again. You should also avoid doing any major changes to their tank until they start eating normally again.

Do not move your fish around too much! This can be very stressful for them and may lead to them not eating.

Keep an eye on your fish and make sure that they are comfortable with any changes you may be making to their tank or décor. Try moving things around slowly over time so that your fish get used to new surroundings.

5. Water Is Poor Quality

If you’ve been noticing that your fish aren’t eating as much as they used to, it could be a sign that the water quality in your tank is poor.

This can also happen if you feed your fish too much protein and too much protein means lots of ammonia!

Ammonia is also formed as uneaten feed or another organic matter in an aquarium decomposes. High concentrations of ammonia in the water make it difficult for fish to eliminate ammonia from their bodies.


Poor water quality can be caused by a number of things that can lead to a variety of health problems for your fish, which may cause them to stop eating altogether.

This can be caused by a number of things, such as:

  • Underpowered Filtration
  • pH Too High or Too Low
  • Too Much Ammonia
  • Overfeeding


Make sure you always keep an eye on the condition of the water in your tank and change it regularly if necessary to avoid any issues with its quality.

You should also go over how often you need to change the water depending on what type of fish you have so that you know when to do so next time around.

To ensure good water quality… test for ammonia, nitrites, nitrates, pH level, and salinity at least once per week using varying types of equipment such as liquid reagents available from the aquarium trade, dip strips, or electronic meters.

6. Incorrect Lighting

When it comes to fish, many owners mistakenly believe that brightly lit tanks are better for their pets. In fact, this can have the opposite effect.

Research has shown that incorrect lighting can put stress on fish and as a result they will stop fish from eating. Lighting that is too bright can also cause fluctuations in the aquarium water temperature.

If you’ve been having trouble getting your fish to eat, it’s possible that the lighting in their tank is not suitable.

The recommended lighting wattage are as followed:

  • 1 to 2 watts of lighting per gallon for fish-only aquariums
  • 2 to 5 watts per gallon for freshwater planted aquariums
  • 4 to 8 watts per gallon for reef aquariums


Check the type of lightbulb you are using in your tank and make sure it is appropriate for the type of fish you have. You should also test how long you are leaving the light on each day – too much or too little light can both lead to problems with your fish eating.

If you find that your current lighting is not right for your fish, try changing to a bulb that emits more or less light depending on what they need. You can also try adjusting the light’s timing to see if that makes any difference.

You should always research what type of lighting your fish need before buying a new bulb for your tank, as only certain types are safe and suitable for use with live fish.

7. They Maybe Stressed

One of the most common reasons why fish stop eating is because they are stressed. This can be due to a number of factors, such as changes in their environment or tank mates.

If your fish seem to be constantly swimming around and avoiding food, it’s likely that they’re feeling stressed out.

When A Fish Is Stressed They May Do The Following:

  • Gasping At The Surface Of Water
  • Strange Swimming
  • Loss Of Appetite


Do your best to create a calm and relaxing environment for your fish by keeping the tank decorations minimal and avoid putting too many fish in there at once.

You should also try adding some plants or other decorations including some hiding stops that will make them feel more at home in their tank.

Make sure you keep an eye on your fish and make sure that they are comfortable with any changes you be making to their tank or décor.

8. Bacterial Infection

If your fish is not eating, has lost weight, and shows other signs of illness such as clamped fins or redness on the body, it’s possible that they have a bacterial infection.

An infected fish will often stop eating as it becomes weaker and less able to compete for food. This can quickly lead to death if left untreated.

Some of the most common bacterial infections affecting aquarium fish are:

  • Nitrite Poisoning
  • Columnaris
  • Fin Rot


Take your fish to an aquarium specialist so they can be properly diagnosed and prescribed the necessary antibiotics to treat the infection.

You should also take steps to improve water quality in the tank as this will help speed up the healing process.

Make sure you finish all of the antibiotics even if your fish starts eating again, as this will ensure that all of the bacteria are killed off.

If you see any of the signs of infection in your fish, take them to an aquarium specialist as soon as possible for treatment.

9. Fish Could Have A Disease

Many fish owners may find that their beloved pet fish are not eating as much as they once were. While this could be due to a variety of reasons, one possibility is that the fish is suffering from a disease.

Just like fish can get bacterial infections, they can also contract diseases such as ich or velvet. These often cause a fish to stop eating and eventually die if left untreated.


Again, take your fish to an aquarium specialist for proper diagnosis and treatment. Many diseases can be cured if caught early enough, but it’s important to seek help from a professional rather than trying to treat the disease yourself.

If you think your fish might have a disease, take them to an aquarium specialist as soon as possible for diagnosis and treatment.

10. Tank Doesn’t Have Enough Room

The size of the tank can also play a role in why your fish is not eating. Fish need plenty of space to swim around and explore, and if the tank is too small they will become stressed out and stop eating.

Too many fish can also have the same effect, this can make the tank cramp and feel like a small environment for the fish.


If you find that your fish are not eating, it might be time to upgrade to a bigger tank. This will give them more room to swim around and eat without feeling stressed out.

Make sure you research the size of the tank needed for the type of fish you have before making any purchases. A larger tank is always better than a smaller one, especially if your fish are not eating.

Fish need plenty of space to swim around and explore, and if the tank is too small they will become stressed out and stop eating. If this is the problem, consider upgrading to a bigger tank.

How Long Can A Fish Go Without Eating?

A fish can go without eating for a period of time, but it’s not healthy for them to do so. Most cold-water fish will be fine for one week without food, however, tropical fish will need to be fed daily.

If you’re having trouble getting your fish to eat, try some of the solutions mentioned above to see if that helps. If none of these work, it’s best to take your fish to an aquarium specialist for proper diagnosis and treatment.


There are many ways to get a fish back into eating mode. One of the most important things you can do is improve water quality by performing regular water changes, and ensuring that there is plenty of dissolved oxygen in the tank for them to breathe.

Adding more decorations such as plants or hiding places will also make your fish feel safer and less stressed out about any potential threats in their environment, so try adding some new décor if they don’t have enough space.

If increasing the size of your aquarium doesn’t work, you could try feeding smaller amounts two times per day instead of one large amount once per day in order to encourage them to eat more often.

You should always take steps quickly when it comes to getting a fish to eat again, as this is often their only chance at survival.