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Dropsy Fish Disease: How to Identify & Treat It Effectively

Dropsy fish disease is a disorder that nearly every aquarist runs into at some point keeping fish. And when it arises it can very quickly kill our cherished pets. So knowing what to watch out for and how to treat it is critical.

Finding a dropsy betta or dropsy goldfish is especially common, given how these fish are often kept in dirty conditions. So what is dropsy fish disease and how to treat dropsy?


What is Dropsy Disease?

Dropsy is one of the most dangerous fish diseases your pet can acquire because it takes a while for any medications to work. And the disease can be fatal within just a few days of the initial symptoms arising. Dropsy always needs to be taken seriously and acted on the moment you see it show up in your aquarium fish.

Dropsy fish treatment can also be complicated because the disease has both an environmental component as well as an internal one. But armed with the knowledge in this care guide you will be able to diagnose and treat dropsy in fish with ease. 

It isn’t a disease that comes up often in clean, well-maintained aquariums. But everyone does have to deal with dropsy disease sooner or later.

Keep in mind also that sometimes a new addition may have a latent case of dropsy that only fully develops when you get your fish to its new home. If a fish was added to your aquarium and develops drops within 1 to 3 days it likely was already on its way to developing dropsy disease.

Dropsy Symptoms in Aquarium Fish

Dropsy symptoms are easy to pick out because they aren’t like many other aquarium diseases. The onset is very rapid as well; sometimes within a day or two what appeared to be a healthy fish may suddenly swell up with dropsy disease. So here are the most common dropsy symptoms to look out for:

  • A large, bloated fish belly from excess fluid
  • Scales that stick outwards, mostly around the belly and sides
  • Swollen eyes (not always)
  • Difficulty swimming
  • Loss of appetite and color
  • Seizures and excess mucus production
  • Rapid death

Why Does it Cause Bloated Fish?

You see bloated fish because dropsy is the result of fluid retention in the abdominal organ cavity of your pet. But this region is meant to house soft tissues, organs, and just a little bit of fluid. There is nowhere for all of the excess to go; a fish can’t simply excrete it as waste. So it just sits in the soft tissues, creating pressure on its insides.

This internal pressure forces the skin to become extremely tight. And as it does so, the scales stick outwards until your poor pet looks like a pinecone. In extreme cases or if you see the disease in small fish, the eyes may even begin to bulge from the fluid pressure. 

This is common with guppy dropsy, glofish dropsy, and other very small fish.

Dropsy Betta Disease and its Causes

If you have a betta or other fish with dropsy then you are likely wondering how it came to be. So what causes dropsy? The disease is an infection of Aeromonas bacteria within the body cavity of your aquarium fish. Normally these germs are found everywhere, even in aquariums with healthy fish and excellent water quality. They even live in outdoor soil and on food.

So normally Aeromonas don’t cause problems for animals. But when living conditions grow foul, such as in an aquarium where maintenance has not been kept up with, these bacteria can reach plague proportions. The immune system of a healthy organism can normally keep up with the constant low-level threat of bacteria trying to invade.

But higher numbers of bacteria make it difficult for the immune system to create the resources it needs to fight on. And the stress created by ammonia, nitrites, and nitrates further tax the body, weakening it right when it needs to be strong. The end result? Dropsy disease and bloated fish. 

So if you see a swollen goldfish or swollen betta the first thing you should be checking is your water quality. Because I guarantee something is seriously wrong with it.

Dropsy causes are almost always high ammonia, nitrite, or nitrate coupled with high numbers of disease-causing bacteria. The bacteria are usually there in aquariums with too much organic waste decaying. This waste can be fish poop, leftover fish food, dead fish bodies, dead plant matter, and so on. Bacteria plus water pollution will cause dropsy in fish.

Is it Dropsy or Swim Bladder Disease?

Dropsy and swim bladder disease are two of the most commonly confused aquarium fish diseases. This is natural because they both have the same alarming symptom: you suddenly wake up to a bloated fish whose distended belly is dangerously big.

Dropsy is caused by internal fluid pressure becoming too severe and stretching soft tissues. But in the case of swim bladder disorder, the cause is due to the internal gasses of this organ. I go into more depth on the function of the swim bladder here in my article on Betta Fish Anatomy.

Like dropsy disease, swim bladder disorder can also be caused by an internal bacterial infection. But it can also arise due to an injury or simply some internal dynamic of the gas concentration that has suddenly become imbalanced in your fish.

The symptoms of swim bladder disease are not just bloating but also the same struggle to swim and maintain proper buoyancy. Fish usually have even more trouble swimming naturally when they have a swim bladder disorder and will bob and float spontaneously. The bloating is usually not as bad as with dropsy disease.

Lastly, the scales of a fish never stand straight out with swim bladder disorder. On the other hand, this is a classic symptom of dropsy disease in fish. 

So look to the scales to tell the difference between dropsy versus swim bladder disease in aquarium fish. And if you can, set up a small, warm quarantine aquarium for a fish with dropsy.


What Causes Dropsy Disease?

While we know that Dropsy Disease is the result of opportunistic Aeromonas bacteria that doesn’t explain everything. Aeromonas are everywhere and typically the immune system of fish keeps them in check.

Aeromonas go from sideliners to deadly threats when that immune response is hampered somehow. Perhaps a fish gets an open wound from an aggressive tank mate. Or, much more often, the aquarist doesn’t keep up with their water maintenance.

Dropsy is not exactly contagious since the bacteria are constantly around. However, the presence of Dropsy indicates that your water quality may be poor, opening up other fish to infection.

Poor water quality is the #1 cause of Dropsy Disease, which is why Bettas, Goldfish, and other fish typically kept in small bowls get it so often. How that manifests ranges from moderate to high levels of ammonia, which is toxic and can kill fish outright, to a constant brew of nitrite and nitrate.

Both of these agents, especially nitrate, are less toxic to aquarium fish. However, Nitrate is particularly insidious because most beginner aquariums don’t have enough denitrifying bacteria to break down nitrate in the system. Nor do they have live plants to take up nitrate as fertilizer.

Instead, nitrate has to be removed by water changes – and if the aquarist doesn’t keep up with them, nitrate is a continuous low-level stressor on the tank’s inhabitants. It will only take another stressor or two – a temperature shock, a wound, pH swing, contaminated food, etc, to allow Aeromonas to get a foothold.

The lack of water changes, nitrogenous waste buildup, and bacterial chow like uneaten fish food (swimming in rotting food is never good) make a nice home for Aeromonas to lurk, waiting for a fish to become stressed or immunocompromised somehow.


How to Treat Dropsy Disease

Once your fish is showing symptoms know that you need to begin treatment ASAP. Dropsy is typically fatal within 1-2 weeks, though the earlier you catch it, the better your chances of reversing it. Once the scales or eyes begin sticking out, you may only have days left to act.

You’ll need to treat both the affected fish as well as the entire tank because Dropsy usually indicates a broader environmental issue like poor water quality. And by “treat the tank,” I mean start with water quality testing and heavy water changes to address these issues. Prevention is by far the best medicine when dealing with Dropsy disease because treatment isn’t guaranteed to save your fish.

Water Tonics for Dropsy Treatment

Adding medicine is only one step in our bloated fish treatment. The second is getting the water conditions where we need them to be. Remember that these bacteria have proliferated out of control because there is too much pollution in the form of organic and nitrogenous waste.

So we need to perform a large water change; up to 50% of your aquarium volume is a good idea. Refill the aquarium with warm tap water treated with a water conditioner and retest the parameters. Have ammonia, nitrite, and nitrate become balanced? If so then feel free to add medication. 

But if these numbers are still high, the pollutants are causing undue stress to your dropsy fish and will make recovery difficult. Perform a second water change, which should then result in normal readings. Unless the aquarium was allowed to become so dirty that it takes more cleaning, that is.

Raise the water temperature of the fish tank as well by 3 to 5℉ for an extended period. Adding more heat will help your fish fight off the infection. This is especially important for a dropsy betta because these are tropical fish that normally live in warm conditions anyway.

If your betta fish that do not have a heater are far more likely to become sick with dropsy disease and other illnesses. So I recommend making a heater a permanent addition to your betta fish tank if it is not already. Bettas will tolerate cold conditions but it is a continual source of stress for these truly tropical, heat-loving aquarium fish.

I also recommend adding a therapeutic dose of aquarium salt to your fish tank. Salt has a slight bolstering effect on the immune system. It also improves gill function by facilitating ion exchange across the cell membranes. 

It does not actually kill Aeromonas, which thrives even in brackish and marine conditions. So don’t think of it as a medication. Consider a little aquarium salt as a great general tonic for a dropsy fish.

Should I Quarantine a Fish with Dropsy?

As we all know, diseases caused by microorganisms can often be contagious, spreading from one sick animal to another. So what happens if we keep a fish with dropsy in the tank with the others. Will you start seeing more bloated fish belly and pinecone scale symptoms arising? Or will they remain healthy?

Dropsy is not exactly contagious in the usual sense. The problem is that bacteria that already live in the environment have become infectious to soft tissues. In other words, the germ can infect your other fish but it is already present in the entire aquarium. 

The issue is twofold: one, that the fish’s immune system has been weakened enough that the bacteria can cause infection. And two, that the bacteria’s numbers have become high enough to break past the natural immunity of your fish.

That said, I actually do recommend setting up a quarantine tank for a dropsy bloated fish. Not because it halts the spread; it won’t. But because it makes caring for the sick fish much easier. 

A quarantine tank has a smaller volume of water that can be tailored to meet the needs of your bloated betta or bloated goldfish. You can raise the temperature higher to help its body fight the infection and add aquarium salt as a general water tonic. 

What’s more, a quarantine tank usually uses a sponge filter or a power filter with no activated carbon, which would normally remove any medications you add to the system. And with no tank mates chasing or picking at the slow, sick fish with dropsy, it has a chance to truly rest and recover its health.

Antibacterial Treatments

As for your sick fish, you’re better off moving them to a quarantine tank for treatment. Antibacterial agents are often broad spectrum and will kill off good bacteria with the bad. If you dose the entire tank you risk resetting your biological filtration capacity, leading to New Tank Syndrome.

Fortunately, not all aquarium antibacterial remedies are harmful to filter bacteria.

API Melafix uses Tea Tree and Cajeput essential oils to not only boost healing but suppress bacterial reproduction.

While it causes the water to foam briefly it smells great and is one of the best remedies for Dropsy and other bacterial diseases around.

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Dropsy isn’t contagious so if you only have a single aquarium you can keep your sick fish with the others. However, it’s harder to provide targeted treatment when dosing the entire aquarium rather than a small quarantine tank. And even medicines can be stressful to fish if not needed.

Give Your Fish a Salt Dip

Next, you need a steady supply of aquarium salt. Even freshwater environments have low doses of salt, which serves many functions.

Salt helps balance fluid and mineral salt exchange through the gills, stimulates slime production in both the gills and exterior slime coat, and boosts immunity. Salt is also stressful for many microbes and parasites.

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To give your fish a salt dip, prepare a separate bucket of aquarium water and four teaspoons of aquarium salt per gallon.

Since the bath will last 15-30 minutes you may want to add more water to ensure it remains warm, depending on your climate.

Carefully net your Dropsy-infected fish and place it within the bucket. Observe the fish as often and as long as possible. You’ll want to watch for any signs of severe stress, like convulsions or shock. Slight shivers are to be expected as the sudden exposure to higher salt concentrations can be irritating to fish mucus membranes.

Once the salt dip is finished, you can return the fish to either the home or quarantine tank. However you should maintain a low level of salt; 1 tablespoon per 5 gallons will provide a background tonic that will aid healing.

Increase Temperatures

Lastly, we should ensure that the tank is warm enough. While bacterial activity accelerates with temperature so too do the immune, respiratory, and digestive functions of fish. Unlike mammals, fish are cold-blooded. We can help boost their life processes simply by turning up the heat when they’re feeling sick.

Temperatures of 78-80F are perfect if your tank typically sits at around 75F. And if your fish are already at 80F, boost this to 84 (so long as your fish are equatorial species that aren’t stressed by these temperatures, like Tetras and Barbs).


Preventing Dropsy Disease in the Future

Remember that Dropsy is a condition caused by rot. And all rot is caused by germs and a lack of cleanliness. We can address cleanliness best by keeping up with water changes so agents like nitrite and nitrate can’t build up to toxic levels.

And when feeding your fish, take care to minimize the amount of leftover food that can rot and lead to problems like ammonia, bacterial growth, and Dropsy.

Lastly, make sure to check on your fish daily and scan them for early warning signs like clamped fins, loss of appetite, or open wounds. Any one of these can help you diagnose a disease more quickly, easing treatment and possibly saving your fish’s life.

Frequently Asked Questions about Dropsy Fish Disease

Dropsy is a disease that can confuse aquarists with how quickly it comes about. And it can even mimic the symptoms of other diseases. So here are a few more tips on how to identify and treat aquarium fish dropsy.

Can a Fish Recover from Dropsy?

Fish can recover from dropsy disease. It is fast-acting and often fatal but if you can identify it before the pinecone scales, swollen belly, fluid retention, and other dropsy symptoms I’ve described here.

How Do You Treat Dropsy in Fish?

Treating dropsy is difficult but not impossible. You need to raise the temperature by a few degrees and medicate your fish with antibiotics that work on Aeromonas bacteria. You also need to perform one or more large water changes before medicating. When you draw water from the tank you remove built-up waste and ammonia. These chemicals are damaging the immune system of your fish and providing food for all of these bacteria to grow out of control.

Does Dropsy Hurt the Fish?

It is hard to say but given how extreme dropsy disease is, it is likely to be painful. Dropsy can also occur in humans and it is widely reported as being extremely painful to deal with.

Is Dropsy Contagious to Other Fish?

Dropsy is not contagious but the environmental germs that cause dropsy can cause it in your other fish as well. So if one fish in your tank has dropsy disease then it is possible for others to get it if you don’t get the bacteria and water pollution under control quickly.


Wrapping Up Dropsy Fish Disease

Overall, finding a dropsy fish is a big challenge for an aquarist to deal with. The onset of the disease is very fast. And if you don’t treat it in the right way, you will lose your fish within just a few days.

But if you act today on the information you’ve learned in this handbook then you have a good chance of seeing your dropsy fish recover and act naturally again.

Jason Roberts
About Jason Roberts
Jason is an aquarium fanatic that has been a fish hobbyist for almost three decades.

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