Guppy Bent Spine – Causes & Treatments

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Humans are not the only ones who can develop a bent spine, unfortunately, fish can too. In fact, amongst guppy fish, bent spine syndrome is a prevalent ailment.

Guppy fish are freshwater fish that are available in many color variations. They have beautiful, flowy tail fins and are an excellent choice for novice aquarists because of their hardy nature.

Guppies can be born with a bent spine or develop it in adulthood. It can be noticed as a curvature in the spine when the fish is viewed from above or the side.

A bent spine in guppies is almost always the result of either scoliosis or fish tuberculosis, and it’s an untreatable condition that often requires euthanasia of sick fish.

If you’re keeping guppies and you’re worried about the bent spine syndrome, in this article I will cover the causes of guppy bent spine, disease outcomes and disease prevention.


Most commonly appearing in the larval or fry stage, scoliosis is a deformation of the spine, whereby the spine develops an “S” or “C”-shaped curvature.

It can also affect adult fish, especially female guppies that can develop it after giving birth, often because of the intense abdominal pressure that appears during this time.

The disease can slowly progress over time or remain stable throughout the lifetime of your guppies. Either way, it’s not reversible and it affects the life quality of your guppy fish.

Fish with bent spine have trouble swimming and they’re often bullied by other fish because of their weakness. The growth rate of your fish is also affected.

The triggering factors of fish scoliosis include:

1.  Inbreeding

In guppies without a large gene pool, inbreeding often results in fry with spinal deformities. This is especially true for new variations of guppy fish that were selectively bred for certain traits.

Diversifying the gene pool and avoiding inbreeding are important elements in preventing guppy bent spine disease.

2.  Bad Diet & Tank Conditions

Guppy raised in overcrowded aquariums with low oxygen levels and guppies kept on a low-quality dry food-only diet can also develop scoliosis.

Guppies are omnivores and require a variety of foods to stay healthy. You should feed guppies high-quality flakes, veggie pellets, spirulina tablets, freeze-dried brine shrimp, freeze-dried blood worms and tubifex.

Also, take care not to overfeed them, which can also cause issues like water fouling and digestive issues.

This all goes to show how important a balanced diet is in preventing diseases, including scoliosis. It’s important to raise your guppies in a well-kept aquarium and avoid aquarium stocking issues.

3.  Hereditary Factors

I mentioned that inbreeding can be a factor in the development of fish scoliosis. In the same vein, another factor that can contribute to guppy scoliosis is allowing fish with scoliosis to reproduce.

Scoliosis can be passed down to offspring. In fact, 90% of fry will inherit the disease from the female fish with scoliosis.

Still, if your guppies with bent spine reproduce and produce sick fry, you should consider reducing their population by allowing them to stay with the adults, which will eat them. Few – if any – guppy fry will survive if left in the same aquarium with adult fish.

Therefore, if your guppies have scoliosis, make sure to prevent them from breeding, because the chances of giving birth to fry with bent spine is inevitable.

Fish Tuberculosis

Fish tuberculosis is a disease that can affect many types of freshwater fish including guppies. In fish, the disease is caused by a bacterium – Mycobacterium Marinum – closely related to the bacteria causing TB.

Fish TB is a highly contagious disease that can be passed onto other fish, other animals and even humans, therefore, immediate action is required.

This disease is common in aquariums that aren’t maintained regularly. Think of aquariums without regular water changes or aquariums that are overcrowded, low in oxygen and high in waste products.

While this is a major triggering factor of the disease, allowing bacteria to grow out of control and thrive, unfortunately, fish TB can appear even in otherwise well-kept aquariums.

This happens when you add new fish that have already been infected with TB to the aquarium (e.g. if you buy them from pet stores, where they have been kept in dirty and overstocked aquariums).

The reason why I’m discussing fish TB in an article about bent spine syndrome is because one of the symptoms of fish TB is a curved or crooked spine.

But then how can you tell whether your fish has TB or scoliosis? Fish TB is also accompanied by other symptoms such as:

  • Loss of appetite;
  • Discoloration;
  • Lesions on body;
  • Folded fins;
  • Protruding eyes;
  • Loss of scales, etc.

Therefore, if your guppy develops a curved spine and exhibits some or all of these symptoms, then immediate action is required because they have fish TB.

Unfortunately, the treatment methods that do exist – antibiotics such as Neomycin, Kanamycin, and Isoniazid – rarely work.

Traditional treatment methods like adding aquarium salt to the tank or raising the temperature of the water hurt more than help (raising the temperature will only lead to the proliferation of the bacteria, aquarium salt does nothing).

The only thing to do when faced with this disease is to immediately remove fish that are sick and humanely dispose of them.

It’s not an easy decision to make, but it’s one that can end the needless suffering of your fish.

Because it’s extremely contagious, it’s highly likely that other fish in your aquarium have already contracted it and it’s only a matter of time until they’re going to exhibit symptoms. Unfortunately, disease prevention is the only efficient tool against fish TB.

Making sure that your fish have a strong immune system by feeding them a healthy and balanced diet and being strict when it comes to water quality, aquarium stocking and providing a stress-free environment can go a long way in preventing guppy fish from getting sick.

Also, quarantining new fish for a couple of weeks before introducing them into the tank is also an important aspect in the prevention of any potentially fatal disease including fish TB.

If after a few weeks your new fish don’t exhibit any symptoms and look healthy, you can introduce them to the aquarium.

How to Euthanize Sick Fish?

Since there is no cure for fish scoliosis or fish TB, euthanasia remains the only option. In fish TB this is always the outcome.

In the case of bent spine syndrome, however, if the disease in not very advanced and your fish can still swim and they’re not suffering or struggling, they can still live a normal life.

Fish that are struggling, getting picked on by other fish (which can further cause injuries and infections), and generally have a low quality of life, should be humanely euthanized.

Although the science is still not in on which is the best way to euthanize fish, there are a few methods that aren’t deemed to be humane and that you should definitely avoid.

Therefore, if your fish are sick and suffering, and it comes to it, do not try to freeze your fish or immerse them into cold water. Same goes for flushing them down the toilet, boiling them or suffocating them, or use carbon dioxide to euthanize them.

These methods are currently not considered a humane way to end the life of your guppy fish. A far better method than the ones I mentioned is adding clove oil into the aquarium.

In high concentrations, clove oil has a sedative effect on most fish, and it works well for guppy fish. If added to the water in the right dosage, it causes your fish to lose consciousness, stops their breathing, and induces Hypoxia (deprivation of oxygen) causing death in around 10 minutes.

To be effective, clove oil must be added to the aquarium at 400 mg per liter dose. You should mix the clove oil with some warm water, which you should slowly add to the aquarium. Adding it all at once will excite your fish, causing further alarm in their state.

After around 10 minutes, you should check your guppies for gill movement. If there is none after 10 minutes, your guppies have passed away, and you can remove them from the aquarium.

Make sure to wear protective equipment when handling fish with TB as the disease can be transmitted to humans via scrapes and injuries.


Because most cases of scoliosis can be prevented along with fish TB, it’s important to make sure that your guppies are kept in optimal conditions and never add new fish to the aquarium without quarantining them first.

But before you can carry out these things correctly, the first important step is sourcing your guppy fish from a reputable breeder that practices correct breeding and doesn’t allow inbreeding between their stock.

I hope that my article has helped shed light on the seriousness of guppy fish TB and guppy fish bent spine syndrome, the ways to prevent it, and the outcomes of the disease.

Updated: January 9, 2022
Questions & Answers
  1. Thank you Fabian! One of my perfect female guppy just started to have bent spine. She’s still swimming and active, but looks like the curvature goes worse day by day, and soon she won’t be able to eat anymore! I’m so heartbroken, and not able to euthanize her! What do you think, does she has any pain bc of the scoliosis? Still I hope she will get healthier!

    1. avatar

      Hey Mihaela! I don’t she will get healthier and most likely she will not get back to normal again. If guppies develop a bent spine during their adulthood, most likely some sort of disease or bad water quality is causing it.
      I’ve seen many cases and most of the time ammonia or nitrite poisoning are the main causes of such spine deformation. I don’t know exactly what is happening with the guppy, but I think that due to poor water quality the fish will have weakened immune system. This will result in getting sick and in some cases the disease will cause deformed spine. Probably you should consider euthanizing her, because things will get worst.

  2. I’ve just got 6 male guppies (with 6 zebra danios) in my 230l tank.

    One of the guppies looks (to me) to have a bent spine since I got him. He was being picked on (lost the end of his tail). He also hid at the top of the tank behind pipes for the first day, but seems to be fighting back and happy now. He was bloated as well, but pooped and is eating again.

    I don’t want to euthanise a healthy fish (especially as he’s my favourite being the underdog). Any advice?

    Would a picture help?

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