Can fish in the fish tank become obese?

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Can fish in the fish tank become obese? Yes, fishes can become obese, and also can die for a cause of obesity. Most fish who die of overfeeding does not actually suffer from any sort of gastrointestinal problems. If your fish is looking overweight or obese, it could be caused by a number of things, such:

  • disease
  • potential tumor
  • overfeeding

Fish look obese caused by Sickness

One of the reasons why your fish may look bigger maybe a disease. The main culprit for freshwater fish is Dropsy. Dropsy causes your fish to become much larger than usual and is often characterized by protruding scales, making the fish look like a pinecone. You may need to quarantine these affected fish or fishes from others, as dropsy can spread. Unfortunately, Dropsy is usually fatal, but you may want to talk to your veterinarian about possible antibiotic treatments that could give your fish a chance of survival. Other possible diseases that can cause enlargement are usually Kidney diseases. Again, you should talk to your veterinarian if you believe that your fish is sick.

Fish in the tank looks overfed because of potential Tumors

Another cause of your fish looking larger and fat may be a tumor. Tumors will usually be uneven and are typically benign. Even if they are cancerous, there are rarely treatments for fish.

Your freshwater fish is obese because of Overfeeding

Sometimes dieting maybe the for your fish looking larger and fat. Often, overfeeding or the wrong types of food can cause constipation and other digestive issues. You can try to feed your fish less or healthier types of food, which varies depending on the species of fish. Overfeeding can also have more serious consequences than digestive once, though. More food means more waste, and overfeeding increases levels of oxygen in the water. If you see your fish gasping at the surface of the water, this means that the water quality is poor and you may need to try reducing the amount of food they are given.

Carrying eggs: If your fish is a female, it may be carrying eggs and not overly fat. Another indication is if your fish has an enlarged vent; this is where the eggs will come out from. If you believe your fish is carrying eggs, you may need to watch to see if she is egg-bound, a condition where she keeps her eggs because the environment is not right for breeding. For her to release her eggs, a male fish has to be present and good water with the right temperature. This varies from species to species. If the fish remains egg-bound, she could become sick and infected.

If the increase in size does not appear to be as a result of any of these factors, it’s possible that your fish is healthy and simply getting bigger. If you have any concerns about the health of your fish, contact a veterinarian.

How Long Can Fish in the tank Go Without Eating

Exactly how long depends on several factors, such as how large the fish is, how old it is, and whether it is a carnivore or herbivore. Large or older fish can go without food longer than small or young fish. It’s a straightforward case of reserves. Large or older fish simply have more body mass and fat reserves they can draw upon. Depending on the species, healthy large fishes like cichlids can easily go 7 to 10 days without food but an aquarium full of baby fish will need to be fed after a day or two. However, a few tricks can be used to extend the interval between meals and still ensure the continued health of your fish.

You can extend the interval between meals by turning the temperature down a couple of degrees putting the aquarium lights on a timer for a shorter-than-normal daytime. A lower temperature will slow the metabolism of the fish, reducing their requirement for food. Shortening the length of daylight helps to limit activity that would otherwise increase the need for food.

 6 signs of overfeeding fish in your fish tank 

Excess fish waste:

It’s worth remembering that what goes in, must come out. If you feed your fish huge quantity of food you will inevitably see the evidence of their super-fast digestive system. Strings of waste attached to the fish’s body is a sign that it has consumed far too much food.

Uneaten food:

Fish quickly eat what they require as soon as the food is dropped in the tank. Anything left after five minutes is surplus to requirements so scoop it out with a net before it starts to break up and pollute the water.


Excess food creates an abundance of algae, an unsightly green or brown slime that can coat the surface of fish tanks and décor. Algae needs food to grow just like any other plant, so when you add large quantities of nutrient-rich fish food to your aquarium, you effectively feed the algae spores as well as your fish.

Sludge in the gravel:

If you do not remove uneaten food straight away, it eventually sinks to the bottom of the tank and starts to decompose in the gravel. Fishes may still try to eat the decomposed food which is not ideal and the rest slips between the pebbles to form a brown sludge that leeches a foul smell into the water.

Smelly Odor:

The combination of rotten food, waste, and bacteria provides a foul-smelling and potentially dangerous environment that can make your water toxic to fish if you do not address the water quality issue and cut down on feeding.

Unhealthy fish:

Poor water quality leads to unhealthy fish and overfeeding will eventually make your fish sick.

Is my fish pregnant or overweight?

Before you can determine if your fish is pregnant or overweight, you have to first be able to tell which one is a female or male. After that, you will check your female fish physical and behavioral changes to know if she is pregnant or overweight.

Identify the male and the female: As a general rule, male fish of live-bearing species are brighter or more elaborately colored and have a narrow, long anal fin on their lower side next to the tail. Females tend to be more drab, with a triangular or fan-shaped anal fin. Some species are more difficult to tell apart and you may need an expert for help.

Physical changes:

To know if your fish is pregnant, watch it every day to see if any physiological changes occur. When a female is pregnant, she develops a lump below the abdomen for 20 to 40 days, indicating her pregnancy as the eggs are formed inside. This is long and round, but can also appear square, especially when she is about giving birth. Females may also have a sort of stain or spot on the abdomen that is shiny black or red, indicating that they are pregnant. That spot is the eyes of the babies and just before delivery they move to the anal area, however, some fish always have this spot, but during pregnancy, it grows darker or brighter.

Behavioral changes:

Notice how the female fish will start to turn shy and will often hide among the aquarium’s foliage and décor. The female will move a lot less than usual during pregnancy. There is also a significant decrease in the amount of food eaten and will not swim as fast as they usually do.

How to keep your fish in good shape and not worry about fish obesity

The first step to avoid obesity is to understand how easy it is to do and how harmful it can be if not done. This will motivate us to develop good and hygienic habits when it comes to our fishes. Try to incorporate the following tips to prevent obesity.

Feed on a schedule:

Most fishes will do well if fed twice daily. If possible, more frequent and smaller feedings are preferred.

Feed the proper amount:

The best way to determine how much to feed your fish is to observe them at periodic intervals while they feed. Add a small amount of food at a time. If all the food is eaten within several minutes, feed a small amount more. The general rule is to only feed them as much as they can eat within 4-5 minutes.

Feed the proper food:

Feeding an improper, poor quality food will not only lead to malnutrition, it will lead to more waste since the fish will not eat it. Choose the appropriate form (e.g. flake or pellet) and the appropriate size based on the tank or pond inhabitants. Some fish will need floating food, while others prefer food that sinks. Research the feeding habits of your fish and feed accordingly.

Remove uneaten food:

Remove uneaten food with a fine net or siphon, these uneaten food decay in the pond and causes and offensive smell and an unsafe environment for fishes.

Can my fish die from overfeeding?

Overfeeding is the major cause of fish loss, it is easy to forget that their appetite is not the same as ours and also, because feeding our fish is the main way we interact with them, they certainly come to expect at least a little sprinkle of food each time we approach their tank and it is hard sometimes not to give in.

However, hungry as they may seem to be, it is important to remember that overfeeding your fish can have serious consequences.

Contrary to popular belief, most fish who die of overfeeding does not actually suffer from any sort of gastrointestinal problem. In fact, the major issue is unrelated to the actual over ingestion of food. Rather, problems occur when excess food is left uneaten and accumulates as waste in the aquarium. The products of decomposed fish food can be extremely toxic and wreak havoc to their aquatic environment.

The recent case study shows, that Zebrafish (Danio rerio) have similar metabolism processes to humans on the matter of gaining weight.

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What can you feed a fish if you run out of fish food?


You can take a break from the normal fish food and feed earthworms to your colorful aquatic pets. Fish love to eat earthworms and these are filling too.


This green leafy vegetable is loved by fish. You can cut the lettuce into small pieces and add in your fish tank. Be careful as some of the fish are allergic to this leafy vegetable.

Boiled rice:

Fish loves to eat boiled rice. Even frozen rice is appreciated by these aquatic pets. Defrost the rice before feeding you’re your fish.


Feed frozen sprouts to your pet, soak the sprouts overnight or boil them before feeding. Defrost the sprouts to ensure good health of your lovely aquatic pet.

Fish fillets:

Predatory fish love to eat frozen fish fillets. Always defrost the fish fillets before feeding. Fatty fish fillets can be harmful to your pet so, choose healthy fish fillets.


Boiled peas are loved by fish. It is one healthy alternative for fish food. Even frozen peas can be used to feed the aquatic pet.

How many times a day do you feed freshwater fish to not overfeed it?

This depends on the fish breed and size. Most fish only require a once a day feeding, though it is better to split it into two smaller feedings. But be aware that a fish will eat even when it’s not hungry. So, there is no point feeding your water-bound pet three time a day, when once a day is sufficient.

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