15 Most Common Guppy Diseases (With Pictures): Prevention and Treatment

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Dealing with guppy diseases is never a fun activity for any fish owner. However, there are plenty of treatments for guppies as well as some prevention measure that can help your fish stay healthy and live active and productive lives.

The one rule of thumb that everyone will always tell you is that “It is much harder to cure a sick fish than it is to prevent diseases in healthy ones”.

If you’re looking for common guppy diseases, causes, and treatment; you are in the right place.

There are a lot of ways to prevent diseases in guppies. Most of these follow good common sense, but it helps to know what to do to keep your fish healthy.

You should keep your water clean and at a healthy temperature at all times. This includes regular tank maintenance and means that you should be performing regular partial water changes.

You should be inspecting your tank on a daily basis to make sure that everything looks healthy. When doing this, if you spot any dead fish, those need to be remove from your tank right away to prevent disease.

If when doing your check you do spot a sick fish; you should quarantine them in a hospital tank, and you should treat any new fish entering the population in this regard as well – making sure they are quarantined for a few weeks before entering the tank.

All of these measures will help you keep your tank thriving and your fish as healthy as can be!

reduce stress

Reduce Stress

While most people probably think of “stress” as a human disease, it can actually have a great impact on guppies as well.

Stress weakens all parts of a guppy’s health and can make it much more susceptible to the various diseases that you will see listed below.

One great way to lower stress in any guppy’s system is to provide them with plenty of places to hide and “explore”. You’ll want to include plenty of live plants in your aquarium along with other things like tree roots or leaves so that guppies have an environment that feels natural to them.

If you are keeping an aquarium that has more aggressive fish than guppies with them, it may be a problem for the group of guppies specifically.

You’ll also want to take all of the preventive tank measures listed above. A tank that has cold water or unstable water temperatures is a big factor that can cause guppies to get sick which will lead you down a much more difficult road when caring for your fish.

Common Guppy Diseases & Treatment

It’s always easier to heal the various illnesses and diseases that guppies get if you are well-stocked with items that can medicate your fish at home. These are the common diseases that can result in death for the guppies that you own.


This is not a common disease for recreational fish owners. If you do think your fish may be in danger of having velvet, it may not be a great sign because it is often hard to spot early.

You’ll notice that your fish may have a case of oodinium if they have gold dust all over their bodies. Some people describe this dust as small dots; but they are extremely tiny and hard to see. It’s important when you’re doing check-ups to inspect your fish quite closely.

One other major problem with this disease is that it spreads very fast. This can be a deadly combination because it is hard to notice and hard to contain. That’s not a good mixture for fish owners who may not be as experienced as others.

The best cure for velvet is a copper medication like Seachem Cupramin. You should note that this medication can kill things like snails or shrimp. You need to read the instructions and make sure that you are careful when adding any substance to a tank.

Another good way to deal with Velvet is to make sure the lights are turned off. This will actually help with the healing and is a good action that you should take right away.

If your fish are healing, it’s important that you are doing extremely frequent water changes as this resists any symptoms hanging around.

White Spots guppy

White Spots – Ick

This is one of the classic diseases that almost everyone who raises fish is pretty well aware of. As long as you provide proper treatment and catch this “ick” in time, this is generally not a disease that will result in the death of your guppies.

Obviously, you will see your fish with white spots if your fish are infected by this disease. You may notice your fish acting a bit strangely as it seems to be bumping into things or swimming right along side the edge of the tank or other decorations. It’s probably easier to note the white spots, but you may also notice that your fish are not as hungry as they used to be.

To cure Ick:

  • Start to up the water temperature gradually – your goal should be around 80 degrees.
  • Use a medication product following their guidelines for use. Seachem Paraguard works really well.
  • Start to put aquarium salt in to your tank. Keep in mind, this may need done to both tanks, not just the infected hospital tank.
  • Increase your normal water changes and try to take a bigger percentage and consider doing them more often.

With these measures, you will decrease the white spots on your fish and they will start feeling healthy. This process usually takes around a week although you may see results faster and may want to continue all of the treatments listed above past the point that you are seeing symptoms in your fish.

Guppy Fin Rot

Rotting Fin and Tail Rot

If you see a guppy that has rotting fins it is due to a bacterial infection. This can be a difficult to diagnose because sometimes the problem is due to bad water among other factors.

The first thing to do is quarantine the sick fish. You’ll need to put it into a hospital tank so that you’re not affecting more healthy fish in your population.

After that, you will want to give your fish an antibiotic or Seachem ParaGuard.

You will need a different medication if your fish has this problem due to fungus or due to ammonia burns, so please pay attention to which medicines will solve which problems.

Swollen Gills

This is a symptom that is caused most often by ammonia. Ammonia is not a chemical to play around with and can make guppies try to get air at the surface of the water. On top of that, it is deadly in the right amounts.

Because this is often caused by things like fish waste, you have to check your tank regularly to fight against this disease.

If you see your fish gasping for air; it’s a likely sign that your water quality is bad. Don’t hesitate to perform a water change and you should probably do an ammonia test immediately as well.

As you are monitoring all of your water checks, it is probably wise to cut back on how much you are feeding your fish. These problems go hand in hand and work together to create a situation where your fish get sick.

Guppy Red Blood Spot

This is a fairly easy disease to detect because of the red coloring that should easily be seen.

The cause of red blood spots will almost always be due to a new aquarium situation. Bacteria live in fish aquariums unseen and can do a lot of wonders for your population. If you introduce too many fish too soon, you’re not letting the bacteria work and create the healthy environment for all of those fish.

If you are introducing fish in the span of a month or less, you will likely see a problem such as red blood spots due to the poisoning.

Be careful when you’re starting out to cycle your water and avoid these invisible killers.

One tool that is useful when checking your water levels is the Seachem Ammonia Alert.  Since you can’t visualize ammonia or nitrate levels, you need a way to check and test if your water is healthy for fish or not.

Guppy Disease (Protozoan)

Guppy disease is named because it almost always affects guppies as opposed to any other fish.

This is actually a parasite that infects guppies and causes problems from there. Initially, the parasite tries to work its way into the guppy’s bloodstream which is where the worst problems can occur.

To prevent any occurrences from ever happening; you need to practice good tank habits. This would include having a regularly heated tank and water changes that are frequent enough to keep the water quality in your tank high.

In that sense, this is usually a preventable disease that should be avoided at all costs.

To treat guppy disease, the first thing you should do is start heating your tank if it isn’t already. This will stabilize your water and prevent any other problems from happening.

After that, you can use a medicine such as Malachite Green. If the disease has had time to strengthen and it is already inside of the guppy’s bloodstream; you may need to go the route of copper medicine and use Seachem Cupramine.

Once you have treated your guppies, it’s important to make sure you are using good tank habits to avoid any kind of flare-ups in the future. Heating your water is usually the best way to stop this from happening again in the future.

Columnaris & Mouth Fungus

Even though fungus is in the name, this is actually something that is caused by bacteria.

You are going to notice this in the mouth area, obviously. You will see a big white area in the fish’s mouth that will give you a warning sign for this disease.

If you do not see this at first, you may be warned by a few other telltale signals that your fish has been infected by columnaris. Your fish will probably have trouble swimming, almost as if it had been disoriented. On top of that, the fish will start eating less and less.

You need to be doing regular tank checks because this disease can turn deadly if not checked on. While columnaris generally is seen in female guppies, it can rarely affect males as well. In this kind of situation, you could be in danger of losing the entire population of fish you have in your tank.

Early detection is a big key here. You want to be on top of a case of mouth fungus as soon as possible which is why you probably need to have medication on hand as opposed to ordering it in or making a trip to get the medication after you see it. That extra time needed to treat the disease could have a big negative impact on your colony.

One chemical that many people use to cure their fish of mouth fungus is Formalin. If not using formalin, then fish owners are probably using aquarium salt to cure their fish. It’s important to note that just because you are adding salt does not mean you get to stop doing water changes. That will still be important for your fish as you heal them.

The biggest thing you can do once you heal your fish of this disease is to keep them in a healthy tank environment. If your fish are in a situation where there are simply too many fish, it might be a situation where you can see re-occurring diseases. Protect your fish by having an appropriate number in any given tank.


The name may be cute, but the disease is not. Dropsy is a disease that will cause your fish to appear bloated. This bloated fish will have problems swimming and may have other problems on the inside such as an infected kidney.

Not only that, but Dropsy is a big killer. You need to take great caution to prevent this disease because once you see it, it is likely too far gone to have any recourse against it.

A lot of stress for an elongated period of time can cause dropsy in guppy fish, so it’s important to provide your fish with a healthy environment with lots of places to “hide” when needed.

Regular care and making sure there is no water pollution is the best tool to fight Dropsy.

Popped Eyes

You see popped eyes in fish for so many different reasons that it can become a losing battle to try to fight for a fish that has this symptom.

Some of these diseases that are on this page like Dropsy can make your fish have popped eyes; or you simply may be in a situation where your tank has dirty water with bad quality.

Popped eyes can actually cause your fish to go blind; but you may actually hurt your fish even more by treating it when you don’t have an answer for what specific problem your fish has.

Swim Bladder Disorder

This is an interesting problem for guppies because you are very likely going to be able to spot the change. The bladder helps control the buoyancy of the fish so if you see a fish out of control, floating at strange angles, or even upside down without reason – this may be what you are looking for.

Ammonia can also cause this problem but usually the culprit is moving a fish from a shallow tank to a deep water tank.

Viral Haemorrhagic Septicaemia

Obviously this is a viral disease that affects guppies. You will notice one of many different signs if you are worried about viral haemorrhagic septicaemia.

The warning signs are:

  • Ulcers or sores
  • Lesions
  • Rotting fins
  • Enlarged eyes
  • Loss of appetite
  • Body that appears darker

The best treatment for a situation where you think haemorrhagic septicaemia is happening is to use API Furan 2.

The most important thing to do after you’ve dealt with a battle like this one is to change your tank water a lot. There’s really not a minimum I would recommend beyond reason to stop the fight against this virus.

Gill Flukes, Gill Worms

This is a disease that can make some uncomfortable because it is actually visible to humans who are looking close enough. What happens here is that a worm is basically attacking the fish and causing problems in the gills.

What that looks like to us is some bleeding in the gills along with a fish that looks like it’s gasping at the surface. Instead of being at the top, your fish may be gathering along the bottom of the tank as well.

This can happen when you rush new fish into your tank population without quarantining them appropriately first. It’s never a good idea to rush when mixing new fish or plants into your environment.

If you are watching closely enough, you may be able to save the population by giving them medication early enough. As this disease progresses, it is deadly to fish and if it is too far gone then you have no chance of saving the fish.

Diana’s Flukes and Sick Guppies (8 pages): Treatments and disease management strategies of skin flukes (Gyrodactylus species) on guppies.

Camallanus Internal Worm

This worm is actually a parasite that can sometimes be found in guppies. Generally, this is seen much more often in outdoor populations than in indoor ones.

On occasion, indoor populations can see this problem but it is believed to be due to feeding live cyclops. If you avoid that; you should avoid this disease that is quite deadly.

You will need to perform a lot of water changes to get your population back to a situation where they will be able to live healthy. You’ll also need to medicate with special medicine known as Levamisole.

Hole in the Head Guppy

Hexamitiasis - Hole in the Body or Head

This is a fancy title that actually means there is a “hole” in the fish. Generally, this is pretty rare and as a recreational owner you will probably never have to deal with it. You may be dealing with hexamitiasis if you see stringy white feces coming from your fish when there is also something noticeably wrong like a lack of appetite.

You’ll need to medicate through food for this disease which could prove to be tricky if your fish are not eating due to a lack of appetite. You’ll need to put medication in the water if that is the case. That medicine is known as metronidazole.

As with most diseases on the list, you will see this pop up due to water issues or crowding issues with the population. Two things that you definitely want to avoid if at all possible.

Bent Spine(Scoliosis)

Scoliosis is basically the same in fish as it is in humans, it is a bending of the spine that is unnatural. Usually this happens due to the way a fish is raised or due to its own genetics.

This isn’t a great thing for your fish to have because they won’t be swimming easily and will cause other problems with a fish’s growth. Your fish can easily inherit this from their mother; so keep that in mind. The good news would be that a fish can live a perfectly fine life with scoliosis, even though it is not ideal.


There are some different methods of keeping fish healthy that come up over and over again when reading about different diseases.

Keeping your tank in great shape is the best way to keep baby guppies healthy. The number one way to keep that tank running smoothly is to perform regular water changes for your fish. You need to be diligent when checking in on your fish to really notice their appearance and their behavior and check for any abnormalities that may clue you in that your fish are sick.

With a good routine, some information, and appropriate medical supplies to help you take action; you should be able to stay on top of any diseases that may hit your guppies and get them back into good health right away.

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Jeff Colt

Jeff Colt

Hello, I'm Jeff- an aquarium enthusiast with over 25 years of experience caring for a wide array of tropical fish, including koi, goldfish bettas, cichlids and more! For me: Aquariums are like jello - there's always room for more!

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