Why Are My Fish Turning Red?

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Written By Fun Fish Tanks

I Love my Fishes 

Have you ever noticed your tropical fish turning red, or perhaps they’ve suddenly died? If so, you’re probably wondering why this is happening.

While there are a variety of different factors that can contribute to your fish turning red, most are due to some sort of water quality issue in the aquarium.

Fishes typically bleed and develop red patches as a result of ammonia poisoning, which burns the gills and obstructs their ability to breathe. One common cause of redness among tropical fish is poor water quality and of course ammonia poisoning. This can occur for several reasons, including overfeeding your fish and failing to perform regular water changes. When waste from leftover food and other debris builds up in your tank, it creates an environment where harmful bacteria thrive and ammonia concentrations rise rapidly

Rearing fishes can be exciting and fun to do. However, they sometimes present a lot of worrying symptoms. Fishes bleed sometimes and it can be so scary seeing the water in your aquarium gradually turning red. Thankfully, fish bleeding is not a hard issue to deal with. Once you get over the fright of seeing blood in your aquarium, the reasons for such bleeding are normally very straightforward.
However, fishes also may tend to bleed due to mechanical injuries in the tank and infectious diseases.

In this article, we’ll take a look at what could be causing the problem and offer advice on how to fix it.

Causes of Fish Bleeding or Redness

It’s already established that bleeding is not normal in fish. Hence, it is a very terrifying sight. However, to know why your fish is bleeding, a lot of factors should be considered including the location of the bleeding. The factors that cause a fish to bleed under the scales will probably differ from the factors that cause bleeding around the fins. Though, some conditions may lead to bleeding in more than one location.

It would help if additional signs such as lethargy and loss of appetite are also observed because they will help in narrowing the long list of diseases and infections down to a small number of options. It might be important to take the fish to a vet. However, one of the causes below will be identified as the reason for the bleeding;

Fish Turning Red Due To Ammonia Poisoning

If your fish starts turning red, it might be due to ammonia poisoning. Ammonia causes fish to lose their appetite and stop swimming. It can also burn the fish’s fins, gills, and skin. Ammonia poisoning is an extremely painful condition for any fish, coral, or plant. Signs of ammonia poisoning in fish include lethargy, increased gasps for air, and redness around the gills.

Ammonia is a common compound in aquariums. It is produced when organic matter decomposes. That includes biological waste products and leftover feed. Ammonia poisoning is a major concern to aquarists due to the fact that it affects the gills and hinders breathing.

If the tank has too much ammonia, the gills may look like they are bleeding. Some additional symptoms to look out for may include labored breathing, lethargy, and loss of appetite. If the ammonia poisoning persists, the red patches on the gills will spread out across the body of the fish. These patches may also be noticed on the fins too.

They are a symptom of external bleeding. If neglected or ignored, the external bleeding may become internal. This may lead to the death of the fish. Hence, a stitch in time always saves nine. Being observant of your fish is very key.

Ammonia spikes in concentration also affect the pH level of the water, which is important for the fish’s good health. The bad pH isn’t just an inconvenience for your fish. It can have disastrous implications on their health if it goes unobserved and unresolved.

Ammonia poisoning can occur when the levels of ammonia in your tank become too high. This can happen as a result of poor water quality, overfeeding your fish, or adding too many new fish to your tank at once.

Ammonia poisoning can cause redness and inflammation among tropical fish, and can be deadly if left untreated.

Another reason for Ammonia to build up at a large scale is if you don’t do frequent water changes to your Aquarium. This will naturally increase the nitrate levels in your Fish Tank thus increasing the levels of ammonia significantly.

  • If your Fish tank is having high levels of ammonia, you should:
  • Monitor the water quality and test the pH Levels of the water.
  • Immediately do a 50% water change.
  • Remove any debris, and organic matter from the Fish Tank
  • Use an Ammonia Detoxifier to neutralize the Ammonia content.
  • Add a couple of more plants in your Aquarium.

Physical Injury

This should be the first diagnosis. Injuries can occur in an aquarium.

An excitable fish may collide with sharp objects in the tank. Aggressive tankmates may also pick on it, causing bruises and bleeding. Bruises from physical altercations are fairly easy to identify.

They don’t look like ulcers caused by infections and the bleeding remains in one location without spreading.

Hemorrhagic Septicemia

This disease is caused by Piscine Novirhabdovirus, a virus that affects aquatic organisms. It’s symptoms are open sores, bruises and inflammation in the gills, and bleeding all over the body.

It may lead to the death of fish if it is not treated urgently.

Bleeding in fish may be alarming, and it is advisable that fish should be taken to a veterinary doctor for a diagnosis.

Is your Fish Suffering from a Bacterial Infection?

Bacterial Infections is another factor to consider when dealing with bleeding in fish. Below are some of the top suspects;

  • Fin Rot: Fin rot is a bacterial infection that is caused by Pseudomonas Fluorescent. Many aquarists blame the disease on poor tank hygiene and stress. Fin rot creates discolorsations the fins , eventually causing them to fray until they fall off altogether (just as the name implies). It can affect the tail as well. Fish with fin rot may develop bloody patches in the affected locations.
  • Dropsy: Dropsy is not necessarily associated with bleeding. Dropsy is quite unlikely to create bleeding on the fishes. However, along with damaging the fins, the disease may cause red spots to appear on fish’s skin, which could be misinterpreted as bleeding.
  • Ulcers: Ulcers are open sores that have the potential of covering the fish’s entire body. Ulcers have a variety of causes. They may include Mycobacteriosis (which causes bleeding due to skin ulcerations), Edwardsiellosis (which causes skin ulcerations), and Vibrio bacteria.The ulcers may appear on the skin, fins, and tail. They can cause internal organs to bleed. Ulcers are very deadly and should be treated with urgency.

Fish are incredibly sensitive creatures that are prone to developing a range of illnesses and infections. For instance, if your fish has suddenly developed Fin Rot, Dropsy or Ulcers, then they may be suffering from a bacterial infection. This type of infection is caused by bacteria that invade the host fish’s tissues and disrupt its normal functioning.

The most common symptom of bacterial infection in fish is lethargy and redness around its body parts, which may be accompanied by loss of appetite, abnormal swimming patterns, and discoloration. If you suspect that your fish has a bacterial infection, it is important to take immediate action.

A fish with a body fungus will have patches of yellow, white or grey mucus covering its body. It usually begins as a small, localized infection, but can quickly spread throughout its body. Symptoms of this disease can vary according to the species of fish.

As the disease spreads, the patches will become more reddish or brown and, at times, the fish’s entire body color may change.

Fin Rot 

Fin rot is an issue that affects livebearers, particularly if they’re kept in warm temperatures. It affects fish fins and tails, causing them to decay or fray. It’s caused by the Aeromonas, Pseudomonas, or Vibrio bacteria, and while it’s easy to prevent, it may be difficult to heal once it occurs.

The most common causes of fin rot are a dirty tank and poor water quality, neglect, or contact with other fish who may have contagious illnesses.

If left untreated, fin rot can eventually kill the sick fish and possibly spread to all of the other fish in the tank.

How to treat your fish for fin rot disease?

  • For the Treatment of the Fish, you should consider water changes, as well as a complete examination of the aquarium’s condition.
  • Remove any waste and debris from the bottom of the aquarium by siphoning out the gravel.
  • Check the water’s pH and temperature levels, as well as make sure it is suitable for your fish.
  • Make sure the water doesn’t have chlorine, ammonia, or nitrite in it, and that the nitrate level is below 40 ppm.
  • Do a 25% water change immediately and then top it up with dechlorinated, freshly-filtered water.
  • You should move the affected fish to a quarantine tank with a different net. This is crucial to prevent the disease from spreading to other fish.
  • Get the appropriate antibiotics for your fish by consulting with a veterinarian that specializes in fish treatment.
  • Following the directions on the product label, treat the sick fish tank with Blue Planet’s Tri-Sulfa Tablets, API Stress Coat, or Melafix or a vet prescribed antibiotic.
  • When an underlying cause is addressed, antibiotics is usually sufficient to eliminate the problem. A medication that works against gram-negative bacteria is advised.
  • Every day, check your fish to see if the fin rot has cleared up.


The disease “dropsy” refers to the swelling of soft tissues in a body cavity, such as the abdomen, as a result of an accumulation of water and other fluids in the Fish. The bacteria causing this condition of Dropsy in fishes is Aeromonas.

The symptoms of this fish disease are typically easy to spot since they include the swelling of the fish’s belly or, in some circumstances, the entire body.

The problem is caused by environmental stressors and/or infections.

Fish that have dropsy frequently exhibit mental and behavior impairments, such as being lethargic, hanging near the top of the aquarium’s bottom rather than swimming around.

How to treat your fish for Dropsy disease?

If the infection is discovered early and the fish is quarantined to enable for appropriate therapy, the afflicted fish can be saved. Follow the instructions below to correctly treat your fish.

  • The sick fish should be removed from the main tank and placed in a quarantine tank.
  • To preserve the health of fish, the temperature of the quarantine tank should be as close to that of the original tank as feasible.
  • It’s time to add some salt to the tank once you’ve isolated the sick fish. 1 teaspoon for each gallon of water in the aquarium is a good amount.
  • And, if their symptoms don’t disappear, antibiotics should be the next choice of treatment.
  • It is simple to put the medicine in your tank. All you have to do is follow the procedures outlined on the packaging of whatever medication you buy.
  • API MELAFIX Fish Remedy – Next use this medication on your Fish Tank. The detailed instructions for use should be given in the packaging of the medicine.
  • The antibiotic mentioned has shown to be beneficial to a large number of aquarium owners. We are confident that many additional aquarium owners would agree with us.


An ulcer is a sore on the top layer of the skin that causes tissue necrosis. They may be caused by a variety of factors, including trauma and parasites. Extreme ulcers can expose underlying muscles due to their severe nature.

If a fish’s immune system is overwhelmed by the bacterial infection, your fish are likely to get ulcers.

There is a danger that a fish’s abdomen can also expose interior organs if it has an ulcer on it. The death of the fish is more probable with deeper ulcers.

While there are several Causes for Ulcers including, poor water quality, parasites, poor nutrition, if you even come across any of the symptoms of ulcers, you should immediately go for treatment of the fish.

Some common symptoms of Ulcers in fishes are Scale loss, Red spots, Increased redness to veins, Exposure of underlying muscles, Skin erosion.

How to treat your fish for Ulcers?

If the Ulcers are minor, your fish is most likely to heal by itself. This means if the Ulcers are small and tiny.

  • However, treatment must be made, if the Ulcers are not improving and getting worse.
  • It is best to consult a veterinarian and treat the Ulcers according to his instructions and advice.
  • Bacterial culture and antibiotic sensitivity test may be used by your veterinarian to identify the causative organisms and a list of antibiotics that are most sensitive to.
  • Do not give your fish over-the-counter antibiotics to treat their ulcers. These unapproved drugs are not tested for purity and effectiveness.
  • Antibiotic medications, prescribed by your aquatic veterinarian, may be required for more severe ulcers that go into the muscles.

Parasitic Disease

Parasites are responsible for several of the ailments that may lead to bleeding. The most common parasitic disease are as follows;

  • Ich: Ich is a disease that causes white dots to appear all over the fish’s body. How it causes bleeding is that Ich causes discomfort (itching) in the fish. In an attempt to relieve that discomfort, the fish will rub itself against objects in the tank. In doing so, it may harm itself, especially if some of the decorations in the aquarium are sharp. A fish with ich can bleed from every visible part of the body depending on how and how often it chooses to rub its body against the tank’s decorations. Bleeding from the fins and gills may occur simultaneously.
  • Anchor Worms: These parasites burrow into the flesh of the fish. This causes bleeding at the location where the worms penetrated the fish. Forcing the worm out will also cause more bleeding.
  • Velvet: This is caused by Amyloodium Ocellatum. Velvet produces a yellow or light brown pigmentation on fish body that looks like a film of rust on the skin. Similar to Ich, it compels fish to scratch themselves against hard objects. This could cause bleeding injuries. It must be noted that velvet causes inflammation and bleeding around the gills. It could hinder the fish’s breathing, and this may in turn lead the fish to break the surface of the water to gulp in oxygen.

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