Fish, like other pets and animals, need to eat every day.
They usually get used to their diets, pick up on the feeding schedule, and anticipate your arrival around their usual feeding hours.
If your fish refuses to eat its food out of the blue, that’s a clue for trouble.
You should start inspecting its environment to discover the problem.
In this article, you’ll find ten possible reasons your fish won’t eat its food so that you can solve the underlying issue.
Fish Not Eating (Top 10 Possible Reasons)
1. Improper Food or Overfeeding
Sometimes, amateur hobbyists buy fish food without reading the labels and considering their fish’s preference.
Freshwater fish and saltwater fish have different diets and need different nutrients.
Even different species of the same category could have distinct dietary requirements.
Make sure you are giving your fish the right food and balance their nutrition.
Second, you should see if the food’s gone bad.
Check the expiration date, and if it has passed, throw it away.
Sometimes, pellets and flakes go bad sooner than expected because they’re not stored in the right container or at the right temperature.
If you open the container daily, you’re exposing all the food to oxygen and moisture.
The food will lose its nutrients way before the expiration date.
It’ll also lose its taste, and the fish won’t eat it.
If you keep your fish food in a damp and warm environment, like above a stove or on the fish tank, the food will rot faster, and the fish will notice.
Maybe your fish are tired of the food you’re giving them regularly.
Based on your fish’s species, you should plan a nutritious diet with a variety of food.
If your fish is carnivorous, include live, frozen, or freeze-dried food in its diet a couple of times a week.
Don’t just give it flakes or plates every day.
If your fish is herbivorous, include vegetables and aquatic plants it might like.
If you’re trying to give your fish a new type of food and they’re refusing to eat it, you shouldn’t give up.
Don’t let them starve either.
Go back to their favorite foods and try again after a few days.
There are a few ways to get your fish to eat the new food.
The most effective approach is to soak it in garlic extract.
The fish will love it and eat it up!
You can either buy liquid garlic extract or make your own.
Another possibility is that you’re overfeeding your fish, and they’re just full!
Most fish need to eat only once a day.
If there’s any leftover food sinking to the bottom of the tank, it most likely means you’re feeding your fish too much.
Uneaten food will turn into waste and reduce the quality of your water.
Research your fish and see what kind of food and how much of it they need as they mature.
2. Bad Water Parameters
Fish are sensitive creatures that sense changes in the water parameters pretty quickly.
Sudden fluctuations in pH, hardness, carbon dioxide, or phosphate levels can make the fish stop eating.
If not discovered and treated, a serious pH imbalance can kill your fish.
That’s why it’s important to check the water parameters with a test kit regularly.
However, some changes in the water can take place over a prolonged period.
Fish urine contains ammonia.
Decaying objects like plant leaves, a corpse, or leftover food can release great amounts of ammonia, nitrite, and nitrate in the tank.
If these chemicals are allowed to build up in the tank, the fish will get more and more uncomfortable, and they may stop eating.
Sometimes it’s just a matter of dirty water.
Dirt and debris can make your water look cloudy and irritate your fish.
In all these cases, regular water changes are the key.
You must replace 10–15 percent of the aquarium water with fresh water every week.
Also, test the water frequently and install a filter if you don’t have one yet.
Remove dead or decaying objects as soon as you see them, and don’t leave uneaten food in the tank.
If you discover an ammonia spike in your tank, keep changing larger portions of the water until everything goes back to normal and your fish start eating again.
3. Wrong Temperature
Unlike humans, fish can’t regulate their body temperatures and rely on the water’s temperature to keep them stable.
Every fish is different, so each one can live comfortably in a specific temperature range.
For a community tank, you should choose fish from similar habitats so that you can provide the right temperature for all of them using a heater.
Maintaining the water temperature without a heater can be challenging, especially if you live in regions where the weather gets too cold during winter.
If the temperature drops below the fish’s comfort zone, its metabolism will slow down.
This will cause it to feel full when it’s actually not.
As a result, your fish will start acting lazy and sluggish and starve themselves unintentionally.
On the other hand, if your aquarium gets too hot, your fish may become hyperactive at first.
However, as time passes, the dissolved oxygen levels in the tank will decrease, leaving your fish to suffocate.
Fish that have trouble breathing are very likely to stop eating.
If your fish is new to the tank, it may be scared by the new environment.
Refusing to eat is normal in this situation.
It should start eating after it’s gotten used to its new home.
Sometimes, a newcomer can stress out the old tenants, but they’ll also get used to their new friend if it’s peaceful and docile.
Lack of hiding places is another potential cause of stress.
Fish need spots like caves, decorations, or dense vegetation to hide in and sleep peacefully.
Moving around the decorations and plants may stress out some species.
This is understandable since you’re changing their comfort zone.
When cleaning the tank, don’t remove all the decorations at once and avoid moving them too much.
You should also look out for external factors that may freak out your fish.
For example, loud noises from the TV or loud music can disturb them.
Maybe even your shadow casts on the tank when you’re trying to feed your fish, and it scares them away.
A crowded tank can also contribute to stress among fish.
Not only will the aquarium need more maintenance, but also your fish won’t relax and eat their food in peace.
You should consider the full-grown size of your fish when purchasing and stocking an aquarium.
Plus, if you house small fish with big ones or docile fish with aggressive varieties, some fish will get bullied when it’s feeding time.
As your fish grow, they’ll get more territorial, especially males.
The bigger and more aggressive ones will compete for food and even chase or harm the smaller ones.
Therefore, the smaller fish won’t come around to eat anymore because they want to avoid getting bullied.
In these situations, you’ll have to provide more food to reduce competition.
If the problem persists, split the fish into two separate tanks: one for the docile ones and another for the bullies.
5. Improper Lighting
The fish’s day starts when you turn on the lights, and they know it’s time for sleep when you turn them off.
If a fluorescent tube of a light bulb breaks or melts, your fish will get confused and may stop eating.
Also, beneficial bacteria grow in the aquariums, providing essential nutrients for your fish.
These bacteria are affected by light and need a specific type of light to grow and thrive, especially in reef aquariums.
Some reef fish species have bolder and brighter colors.
Well, that’s not their true color made by skin pigments.
Those are actually beneficial bacteria which live on their bodies and provide nutrients.
They have an important relationship that benefits both of them.
If the bacteria don’t get proper light, your fish will feel sick and stop eating.
This is why you should install the right lighting systems for your tank to provide the specific light spectrum for the bacteria’s survival.
During pregnancy, fish feel a bit insecure and uncomfortable around other fish.
This stress can cause them to reduce their food consumption, but right before giving birth, most pregnant fish will eat less or stop eating altogether.
Their abdomens will swell, and you can see a dark triangular mark on their belly, near the lower fin.
You can sometimes see the fries’ eyes through the fish’s body.
If you notice any of these signs, put the pregnant fish in a breeding tank, where it can be alone and give birth in privacy.
7. Electrical Current
It might sound unlikely, but your water could have an electrical current running through it!
The current source could be a heater, powerhead, or any other electronic device you put in the water.
Over time, the heater’s seal may get damaged or cracked, and a bit of water can get inside.
Fish are susceptible to electrical charges, and they may stop eating or moving if they sense anything.
Sometimes you’ll feel a buzz when touching the water, or your arm hair may stand up.
You might not even feel the current yourself, but the fish definitely will.
Use a multimeter to measure the electrical charge in the tank, and then, find the source and remove it.
Different health issues can kill your fish’s appetite.
For example, Dropsy is a fatal illness caused by poor water quality, stress, or low-quality food.
The fish’s abdomen will swell, causing its scales to stick out, and it’ll also stop eating.
Another common illness is Fin or Tail Rot, where the fish’s tail or fins become frayed with white edges.
This will cause the fish to stop eating and stay at the bottom of the tank.
Poor water quality or bullying can trigger this condition.
Swim bladder disorder and constipation can also happen, especially to fish with egg-shaped bodies.
Loss of appetite, difficulty in swimming, and floating to the surface are its symptoms.
Many other illnesses can cause your fish to lose its appetite, become sluggish, hide, or lie at the bottom of the tank.
Sometimes, these symptoms are simply due to old age.
It’s a good idea to quarantine the fish with signs of sickness and bring it to a vet for treatment.
By introducing new fish or plants to the aquarium, you might inadvertently introduce harmful agents like bacteria, fungi, viruses, protozoa, worms, and crustacea into your tank.
These microorganisms often cause contagious infections, especially if your fish’s immune systems are compromised due to poor water quality, inefficient diet, or stress.
Your fish will stop eating if the infection spreads and leaves them feeling hopeless.
Cottonmouth is a common bacterial infection which manifests as white spots around a fish’s mouth.
Fungal infections are pretty common in aquariums, too.
With these infections, a white cotton-like growth will spread on the fish’s skin, fins, mouth, and even gills.
This disease is extremely dangerous and can wipe out your entire tank if left untreated.
Most infections can be treated with big water changes and prescription medicine—provided the problem is diagnosed correctly and on time.
Parasites are single-celled organisms called protozoa which are invisible to the human eye.
You won’t notice them unless your fish are infected.
Parasites attach themselves to their hosts, so they can use their nourishments.
This makes the host very sick, so they’ll refuse to eat.
The condition known as ich or white spot disease is a common parasitic infection that is fatal to fish and can infect your whole aquarium in no time.
It appears as white spots all over a fish’s body.
There are multiple steps you should take to clean your tank from the ich.
Slime diseases and Velvet are other parasitic infections which can irritate your fish to the point of starvation.
Significant water changes, appropriate medications, and increasing the temperature are things you can do to defeat parasites.
Frequently Asked Questions
1. What Do You Do If Your Fish Isn’t Eating?
If your fish isn’t eating, first check the food and see if it’s past the expiration date or smells bad.
Then try to give your fish its favorite meal, like live food for predators. If it still doesn’t eat, check the water quality and parameters.
Ensure the pH, hardness, carbon dioxide, phosphate, ammonia, nitrite, and nitrate levels are all under control.
Then, check the water temperature to make sure it’s not too hot or too cold.
Also, rule out stress, bullying, pregnancy, inappropriate lighting, and electrical current in the water.
If none of these steps helps, look for signs of sickness, infections, or parasites and get a vet to look at your fish.
2. How Do I Know If My Fish Is Starving?
To know if a fish is starving, monitor its behavior.
Some fish make it very obvious that they’re hungry by swimming near the glass, repeatedly looking at their owners, or gulping for food at the surface.
Some fish may dig around the substrate for food.
Your fish may start acting aggressively towards other fish when it’s hungry, or it might become lazy and sluggish, standing in the corner without moving.
You may even notice that your fish has lost weight.
3. How Long Can Fish Go Without Eating?
Almost all fish can go for two or three days without eating.
The bigger the fish, the longer it can withstand food deprivation.
Some fish can survive for up to two weeks without eating, but you shouldn’t starve your fish that long.
If your fish isn’t eating, find out why and solve the problem so your fish won’t become weak.
4. Why Is My Fish Spitting Out His Food?
Fish can sense if food has gone bad.
Fish food isn’t usually properly stored in stores or at home, so the shelf life is shortened before you even buy the food.
When you keep the food in a humid place and open the container every day, exposing the food to oxygen, you’re speeding up the rotting.
Keep the food in air-sealed containers or zip-lock bags and put it in a dry place to keep the nutrients and taste locked in.