It’s easy to fall into the trap of overfeeding fish as a treat. Unfortunately, this usually does more harm than good. But can fish die from overeating? While not all fish are prone to excessive eating, it can sometimes happen.
Overeating food is a common cause of death in fish. If fish are allowed to eat more than they should, they can develop life-threatening conditions, such as fatty liver disease, fin rot, obesity, and constipation. Signs that you’re overfeeding fish include fat fish, low water quality, dangerous pH, oxygen and ammonia levels, and a build-up of algae.
If you have multiple fish species in your tank, larger fish may overeat all the food, causing smaller fish to starve to death. If you notice your fish are becoming too fat, it’s probable that you’re overfeeding your fish.
Do Fish Keep Eating Until They Die?
Most fish species only eat until they feel full. However, fish that live in the wild don’t know when their next meal will come, so they eat more than they need to keep themselves full. This is usually followed by days of going hungry until they find more food.
As a result, some fish, including those in captivity, are hard-wired to take whatever food comes their way, even if it’s too much. Whether fish die from overeating also largely depends on the food that’s being given to them.
Dry pellets and flakes expand when wet. If fish swallow them while they’re still relatively dry, the food will expand in the stomach instead of in the tank’s water. As a result, some fish die as their digestive system collapses under the strain.
Not all fish die as a direct result of overeating. Many problems arise from eating too much or too much food being present in the tank.
How Do Fish Die From Overeating?
These health issues are all caused entirely or indirectly by overeating:
Fatty Liver Disease
Fatty liver disease is also known as hepatic lipidosis, and most commonly affects African cichlids and rainbowfish.
MSD Vet Manual describes how it’s caused by a high percentage of carbohydrates in the diet, which is a common symptom of overeating. Excess feeding of high-fat foods is another cause.
As a result of fatty liver disease, fish can become unwell and eventually refuse to eat as their digestive system fails. In the worst cases, death is likely as the liver can’t function properly.
Fin rot is an infectious disease that’s caused by several species of bacteria. While it’s easy to treat, the most common causes are environmental and almost always involve stress. Overeating also triggers the condition. Other causes include:
- Dirty water
- Aggressive fish
- Injury to the tail and fins
- Handling by humans
- Environmental disruptions
Fish with fin rot display the following signs:
- Discoloration on the fins
- Milky edges
- Fraying of the tail and fins
- Ragged edges where pieces of the tail and fins fall off
- Red and inflamed patches
- Secondary fungal infections
As described by Proceedings of the Indian Academy of Sciences, fin rot is aggravated by overcrowding and dirty water, which excess feces contributes to. Overeating causes fish to poop more often, tainting the water’s quality and increasing the risk of ammonia.
If fin rot isn’t treated, affected fish die. Antibiotics can clear the problem, but fish mustn’t be allowed to overeat, or the condition may return.
Fish develop constipation when they overfeed on flakes and pellets, particularly on low-quality varieties that don’t contain enough fiber. Constipation causes uncomfortable bloating and stringy feces.
Constipation can have devastating consequences if not treated, and quickly and unexpectedly leads to death.
To treat constipation, fish must be fed green foods that provide fiber. Healthy green foods and vegetables include:
- Tinned peas
- Blanched curly lettuce
- Sweet potato
You’ll also need to reduce your fish’s flake and pellet intake to reduce unhealthy overeating.
Will Fish Eat Until They Explode?
It’s highly unlikely that fish will explode from overeating. However, it is possible for small fish to eat so much food that their bellies and digestive systems rupture. This is a direct consequence of overeating.
Some fish, like the common goldfish, don’t have the receptor in their brains that tells them when they’re full. As a result, they’ll eat all the food inside the tank, even if it’s too much for their small digestive systems.
This usually takes place over a long time, as the digestive organs become unable to cope with the amount of strain placed on them. You’d have to overfeed your fish significantly for them to explode, but this is easy to do.
Similarly, constipated fish are more likely to develop problems, as the waste has nowhere to go, instead of building up inside the gut.
That being said, a lack of appetite is a common side effect of constipation, so your fish would probably stop eating before exploding themselves.
Therefore, it’s an owner’s responsibility to only provide the amount of food your fish needs. You might wish to treat your fish to extra food, but doing so can kill them. If you’re unsure, speak to a fish expert, who can guide you.
Overfeeding Fish Symptoms
Overfeeding causes as many problems as overeating. When too much food ends up floating in the tank, it disrupts the tank’s ecosystem, resulting in a dangerous imbalance that causes the fish to become unwell. Signs that you’re overfeeding your fish include:
- Cloudy water
- Food at the bottom of the tank
- Dirty gravel
- Low pH
- Pellets and flakes floating in the water
- Fat fish
As a result, the following issues will occur:
Poor Water Quality
Overfeeding results in excessive amounts of decaying matter in the aquarium. Fish don’t eat rotting food, so it lies inside the tank, decomposing and releasing ammonia and nitrites into the water.
Similarly, fish that have overeaten will poop more, adding to the amount of decaying matter in the tank. When ammonia rises to harmful levels, it causes poisoning, leading to a slow and painful death for fish.
Low Oxygen Levels
Decaying food is an aerobic process. The process uses lots of oxygen and produces high carbon dioxide levels, resulting in a lack of dissolved oxygen inside the tank.
As a result, fish may struggle to breathe and spend most of their time at the tank’s surface to find oxygen. Their gills will also move more vigorously, as they attempt to increase their oxygen intake.
Affected fish tend to swim less and may float about in the tank, as they have no energy to move about.
Algae In The Tank
Too much food causes an abundance of algae inside the tank that coats the tank’s surface and gravel. When uneaten food is left in the tank, algae spores feed off the nutrients, causing them to grow quickly. This is an easy way to tell that you’re overfeeding your fish.
You’ll need to clean the algae off the tank’s surfaces before it causes a spike of harmful ammonia and nitrites.
As well as a build-up of algae, dirty water emits a foul odor that many fish owners find unpleasant.
Rotten food attracts harmful bacteria that build up quickly inside the tank. Along with raised ammonia levels, the tank will begin to smell unhealthy due to decaying organic matter.
How To Prevent Overfeeding Fish
If your fish are putting on an excessive amount of weight, it’s time to look at how to prevent overfeeding. If you don’t, fish can develop a range of health problems that will eventually cause them to die. To stop yourself from overfeeding your fish, follow these steps:
Stick To A Schedule
Most fish respond well to a twice-daily feed – one in the morning and one in the afternoon. However, some fish prefer smaller feedings more often throughout the day.
It’s up to you to monitor your fish’s eating habits and decide which schedule they respond best to. Once you’ve decided on one, stick to it. That way, fish will know when they’re going to be fed each day. This makes the fish less likely to overfeed, as they know food is coming.
Measure The Food
We’re not necessarily saying to weigh food with scales, but measure the amount you’re feeding your fish.
Once you’ve placed an appropriate amount of food into the tank, observe your fish to see how much of it they eat. Time how long it takes them to consume everything.
If the fish eat all the food in under four minutes, you may not have given them enough. Try adding a little more into the tank so that scavenger fish who prefer to eat more slowly get a chance to eat.
Also, feed to the number of fish in the tank, not the tank size. This is a common mistake that many fish owners make.
Separate Different Fish Species
Different fish species have different eating habits. Some dominate the tank, particularly at feeding time. Some fish need excess amounts of food and will eat what’s available without giving smaller fish a chance.
As a result, it might be time to rethink the set-up of the fish inside the tank, separating the big fish from the small.
Feed A Quality Diet
To ensure your fish receive optimum nutrition and aren’t overfeeding on junk food, provide high-quality flakes or pellets that are packed with vitamins and minerals.
High-quality feed also keeps your fish full for longer, eliminating overfeeding caused by hunger.
How Much Should I Feed My Fish?
Freshwater fish are slender in appearance, so it’s easy to tell when they’re overeating food. What’s not so easy is knowing how much to feed them.
All species of fish have different food requirements. But as a general rule, providing enough food that allows fish to eat everything within five minutes is about right. Or, if you’re looking at the amount to feed per fish, aim for 30 seconds to one minute of non-stop eating time.
If in doubt, underfeed. Uneaten food falls to the bottom of the tank, where it decays and rots, causing a spike in harmful ammonia levels if left for too long. Ammonia poisoning is often fatal.
If you have fed your fish too much food, remove all traces of waste from the tank as soon as you can. You don’t want to give the food a chance to decompose. Fish also won’t touch old, rotting food so that they won’t go back for it later.
One of the worst things you can do for your fish is to overfeed them. You might feel like you’re doing them a favor, but greedy fish or fish that aren’t in a regular feeding schedule will eat as much as they can to prevent starvation, even if they’re due another feed on the same day. To avoid these fatal health conditions, limit the amount you’re feeding, and monitor your fish’s behavior.