Bent Spine in Fish – Causes and Prevention

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As a novice fishkeeper, you are bound to make mistakes and face unexpected situations that you may not know how to handle. One of these situations relates to fish health, as fish can encounter a variety of health problems along the way.

These come with numerous symptoms, many of which are similar, causing confusion regarding the underlying health problem.

The bent spine syndrome is one such symptom that typically suggests a life-threatening condition.

Today, we will discuss the causes, treatments, and prevention strategies relating to bent spine syndrome to shed some light on the matter.

Causes of Bent Spine in Aquarium Fish

A bent spine is always a reason for concern, given that it signals the presence of an often incurable condition.

Some of the primary causes for a bent spine include:

– Scoliosis

Unfortunately, scoliosis is an incurable condition, but this doesn’t necessarily mean that the fish requires euthanasia. Some fish can live with scoliosis so long as the condition isn’t too severe; there are degrees, you see.

Simply put, scoliosis is a deformation of the spine, forcing the fish’s back into an S or a C position.

This will affect the fish’s swimming and movement as a whole, eventually causing discomfort and pain the more the disorder progresses.

There are several triggers to consider:

  • Genetic factors – Scoliosis is a genetically-transmitted disorder in most cases. This means that the condition is more prevalent among larvae and fry. You can usually tell that your fish has scoliosis early on, so you can decide if euthanasia is the way to go before the disease aggravates. Which it does in most cases.
  • Improper water conditions – Ammonia, nitrites, and high nitrate levels will often contribute to scoliosis and several other health problems. Your fish need a clean environment with stable chemistry to remain healthy over the years. Always have a detailed maintenance routine written down to prevent health issues that can aggravate with time.
  • Improper diets – Most fish require a diverse meal plan for proper nutrient intake. Diversity is the key, as it prevents nutritional deficiencies and keeps your fish healthier and happier. Meal frequency is also important here. Too little food leads to nutritional deficiencies, while too much causes digestive problems and fouls the environment. Most inexperienced aquarists deal with the latter, as they often overfeed their fish. This is proof that the road to fish Hell is often paved with good intentions.
  • Inbreeding – This is probably the most widespread cause of bent spine among inexperienced aquarists. They lack the know-how to properly manage the fish’s breeding season, which leads to inbreeding problems in most cases. That’s because the fry resulting from one pair cannot leave the area, given that they live in a closed environment. So, they will eventually practice inbreeding which is known to produce a variety of genetic problems, inbreeding being one of them.

As you can see, some scoliosis problems are preventable, while others are not.

– Tuberculosis

This condition is even more dangerous than scoliosis, despite being more preventable.

The main problem is that fish tuberculosis is untreatable and highly contagious, capable of spreading within the fish community fast.

The culprit is Mycobacterium marinum, a bacterial organism that’s more prevalent in environments with dirty waters and a lack of proper maintenance.

The afflicted fish will display a variety of symptoms like lack of appetite, discoloration, protruding eyes, loss of scales, body lesions, etc. Some will even gasp for air and exhibit breathing difficulties due to low water oxygen or gill tissue damage.

The curved spine is generally a sign of advanced tuberculosis, at which point euthanasia may be the better option.

No treatment works against fish tuberculosis, so you’re only left with prevention as the only management strategy.

Once your fish has contracted tuberculosis, remove the victim from the tank immediately and euthanize it humanely.

– Physical Injury

Physical injuries are often known to produce the bent spine effect due to the bacterial infections associated with these episodes.

Most of the injuries occur due to the fish’s interactions with sharp or rugged elements decorating its tank.

Even minor cuts or skin lesions can serve as a gateway for various bacteria and parasites that can infect the fish.

Rough play or bullying is also a concern. Mixing fish of different temperaments and sizes is a sure way of increasing the risk of physical injuries.

Sometimes, the powerplay among fish is different than you might expect, as the smaller fish often cause the biggest problems. Pea puffers are the best example in this sense.

While they barely reach 1 inch in size, they are very feisty, territorial, and aggressive, especially towards large-finned fish like guppies and bettas.

Fin nipping is a serious problem because of it, as even the smallest fin damage can infect fast.

How to Prevent Crocked Spine in Fish?

To prevent bent spine syndrome, consider the following tips:

  • Pristine tank maintenance – Your fish should always be housed in clean and healthy waters. Have a filtration system in place, vacuum the tank substrate regularly to remove fish waste and food leftovers, and perform at least one partial water change per week. These maintenance strategies should become part of your tank cleaning routine. Also, get a water tester kit to make sure you detect any chemical changes in the water fast.
  • Proper diet – Each fish species comes with its own dietary requirements. You should always house fish with similar food requirements to make feeding easier. This way, you will only need to focus on one meal plan instead of 2 or more. Always keep in mind that diversity is key when it comes to fish feeding. Combine live foods with various veggies and plant-based foods for a well-balanced diet over the years. Some fish may even require vitamin and mineral supplementation if their normal diet isn’t enough.
  • A safe layout – If your fish requires the presence of rocks and various aquatic decorations, always choose safety above esthetics. Avoid rocks with pointy or rugged parts, and the same goes for any other aquatic element. Also, avoid using aquatic decorations that aren’t meant for that. These may contain paints or chemical contaminants that make them unfit for tank use.
  • Compatible tankmates – Make sure all of your fish are of similar size with similar temperaments, requirements, and dietary preferences. The more your fish are similar, the more stable and stress-free the aquatic community will be. Naturally, this is just general, not universal advice. Some fish hate being housed with similar-looking fish, for instance, which can cause them to turn violent as a result. But, other than that, all other markers should be as close as possible.
  • Get a breeding tank – You want to prevent inbreeding which is one of the primary causes of scoliosis. Get a breeding tank, set it up according to your main tank, and move the breeding pair there until the eggs are out. Then you can relocate the parent fish into the main tank so that the fry can grow in peace. This is especially important if you plan on increasing your fry’s survival rates, as most fish are cannibalistic. If you’re looking for selective or commercial breeding, you need multiple breeding tanks to separate the different fish generations. This is critical when pursuing specific physical features and circumventing inbreeding.
  • Source your fish carefully – Most commercial fish sellers keep their fish in suboptimal conditions, often overcrowded and on poor diets. It’s common for people to get their fish already sick, although they have no obvious symptoms at first. You can’t know if the fish you’re getting are inbred or already deal with infections or parasites. To circumvent this issue, always source your fish from professional breeders with a good reputation on the market. Also, quarantine your fish for at least 2 weeks upon arrival before adding them to the main tank.

Lastly, keep in mind that you cannot prevent unexpected and random genetic faults that can happen between generations. Some fish will simply develop scoliosis, and there’s nothing you can do to avoid it.

Fortunately, the condition is visible as early as the fry stage, allowing you to cull the sick immediately.

Can You Treat Bent Spine in Fish?

Unfortunately, no, you can’t. You can resort to palliative care to minimize your fish’s suffering, especially if the condition isn’t too severe.

But, if it is, I recommend euthanasia. I realize this makes for a difficult choice, but you’d be doing your fish a favor.

Extreme bent spine causes pain and discomfort and prevents your fish from living a quality life.

Can Fish Live with Bent Spine?

It solely depends on the condition’s nature and severity. Some fish die fast due to the disorder aggravating or causing additional damage, while others can live longer.

The problem is that bent spine syndrome always aggravates with time. The only thing that differs is the progression speed.

In essence, fish with bent spines swim slower, causing them not to eat properly and become targets of bullying from other fish.

If euthanasia isn’t an option at first, it should become one as time passes.

Should You Euthanize Fish with Bent Spine?

I would say yes, you should euthanize them. If your fish has a bent spine, the situation is severe and will only worsen with time.

I say timely euthanasia will save the fish from a lot of suffering, even though it may be a difficult decision to make.

If you can’t euthanize the fish yourself (I’ve written comprehensive guides on how to do that, by the way), ask for a vet’s help.

The professional will euthanize the fish humanely with as little suffering as possible.


The bent spine syndrome is always a symptom of a more severe underlying disorder.

Fish displaying signs of a bent spine rarely live several months past the diagnosis point.

Do your fish a favor and give them a humane passing to save them from all the suffering they are bound to endure otherwise.

Author Image Fabian
I’m Fabian, aquarium fish breeder and founder of this website. I’ve been keeping fish, since I was a kid. On this blog, I share a lot of information about the aquarium hobby and various fish species that I like. Please leave a comment if you have any question.
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