sick goldfish

GoldFish Diseases and Ailments

Goldfish Diseases and Treatment

Goldfish are surprisingly a hardy breed of fish and usually do not get sick.

If you have taken the preventative measure of maintaining good water quality, then it may be time to determine what has caused your fish to be sick.

How do I keep my fish from getting sick?

Preventative Measures to Have Healthy Fish

  • Test Water Weekly

  • Feed a healthy, varied nutritious diet

  • Use a good filter system to filter waste and toxins

  • Don’t overcrowd; two fish maximum for every twenty gallons of water

  • Have a hospital tank ready in the event you need to quarantine a sick fish

What causes goldfish to get sick?

  • Poor Water Quality is the  #1 cause of sick fish
  • Poor Diet
  • Overcrowding (too many fish)
  • Handling the fish
  • Incorrect water temperature
  • Adding new fish that were not quarantined for two weeks. New fish can be carriers of parasites and other sickness’

Poor Water Quality

The very first thing to check if you have a sick fish is the water quality. Make it a priority to

keep your fish tank clean and healthy. Test your water regularly.

Important to Remember

  • Clean and Clear Water is BEST...Murky Green Water is BAD!
  • Fish Bowls are merely containers that are too small for fish and is nothing more than a confined container for polluted water. It is highly recommended not to use a fishbowl if you want your fish to live.
  • New Fish: never put a new fish directly into your existing fish tank. Always quarantine them in a hospital tank for two weeks. Parasites on the new fish will infect your entire tank and make your other fish sick as well.
  • Overfed fish produce more waste. More waste produces polluted water.
  • goldfish cannot survive without a filter system.
  • Don’t overcrowd your tank; two fish for every twenty gallons of water at the minimum. Overcrowding tanks cause more waste than the tank can handle. A certain amount of space in the tank is required per fish because of the oxygen content the fish requires. Too many fish depletes the supply of oxygen.

Process of Elimination: What’s Wrong with My Fish?

If your water quality is good and you can’t figure out why your fish is acting strange or is sick, there are ways to figure out what may be causing it and how to treat it. It is usually a good thing to consult with your local aquarist or pet supply if in doubt.

1.  What are your fish’s symptoms?

  • Appearance
  • Color
  • Behavior (rubbing up against things, laying at the bottom, floating upside down, etc.)

2.  Assess your water quality.

  • Test the water
  • Check filtration system to ensure it’s working correctly (if filtration isn’t working right, oxygen levels can drop)
  • Check water temperature. Drops in temperature can cause fish to get sick.

3. Common Behavioral Symptoms

In this section of the article, I will go through various behavioral symptoms and explain why your fish may be exhibiting them.

Let’s begin.


If your goldfish is hanging on the surface of the water and is appearing to ‘drink’ the air, it is called gasping.

Goldfish also suddenly dart up to the surface to take a quick gulp and then continue swimming. 

If your fish is gasping, it means that there’s something wrong in the tank---which is usually the quality of water. 

Other reasons include there being insufficient water agitation, the tank space not being able to provide enough oxygen for the goldfish to breathe, ammonia, pH, or nitrite levels being out of balance, etc. 

If your fish had the come to the surface to gasp some air, it means that the gills are damaged due to parasitic infestations or even store-bought medications.


The biggest sign of healthy goldfish is that they are perky and like to move around most of the time.

They enjoy foraging around the bottom of the tank to look for food, and explore their environment constantly. 

If your goldfish seems uninterested, weak, droopy, and sad, chances are that she isn’t well.

Some lethargic goldfish hang listlessly at the surface of the water and even sit on the bottom of the tank. 

They generally seem depressed and aren’t really concerned when other goldfish start to nibble at them. 

If your goldfish shows any signs of lethargy, the first thing that you should do is to check the water.

A change in the pH or other irregular parameter changes is probably occurring in the tank.


Some call it goldfish suicide which is incorrect. 

If your goldfish is jumping out of the tank, it is trying to relieve the discomfort caused by poor water quality or parasites. So, it’s the fish’s way to escape the bad environment for a while. 

Before making the big leap, most goldfish show erratic behavior such as scratching on objects, darting around frantically in the tank, or even twitching spasmodically.

In all, if the antics continue, the goldfish may end up on the floor.

But, disease or water quality isn’t always the culprit. 

In some cases, females leap from the tank to escape the pursuit of male goldfish during breeding season! 

If you have an aggressive goldfish that may be bullying the others out of the tank, you can separate the aggressive fish from the rest of the tank to make sure that’s the case. 

What about the fish that have jumped out of the tank?

You shouldn’t give up hope! In some cases, you can revive your goldfish by placing it back in the water again.

You can try this if your fish isn’t completely dry and it’s only been under 60 minutes since the fish jumped. 

You can work open the gills gently using your fingernails in case they have been dried shut. 

If you have wood or tile flooring underneath the tank, the jumper fish is more likely to survive as the water that comes out with the fish helps keep it moist longer than other surfaces. 

Don’t try to put a goldfish that has gray eyes, skin cracks, concave eyes or is not intact back in the water.

4. Sitting on the bottom of the tank: 

Goldfish that rest on the bottom of the tank are probably not getting the rest that they need.

Healthy goldfish are known to remain active almost all the time. However, if your fish looks like she doesn’t have much life left in it, you need to check some things out. 

If your goldfish sitting at the bottom of the tank leans to one side she may also clamp the fins and show other signs of health issues.

If your goldfish is sitting at the bottom with a red belly, it’s beyond the point of recovery.

But, why do goldfish bottom sit?

The most common explanation is that the fish is having problems with the water quality. But, in some cases, swim bladder may be the cause, and it is simply a matter of constipation.

Yes, goldfish, too, get constipated! 

If a goldfish is constipated, it’ll scoot along the bottom of the tank when it is startled, instead of mustering up the strength to swim normally as a goldfish affected by nitrite poisoning does. 

If you think your goldfish is constipated, you should try the frozen pea diet for a day or two until your fish regains proper swimming habits.

5. Flashing: 

What does flashing mean? 

A flashing goldfish dashes around wildly and suddenly in the tank.

The fish may also sometimes roll over her side to rub on the substrate, careen into the tank decorations, or even hit its face on the corner of the tank wall. 

This all seems like the goldfish is having a fit.

When a Goldfish flashes, it merely means that it's itching itself---something similar to how you react when a mosquito bites you. 

This makes their movement seem erratic and uncontrolled because they don’t have tiny hands. 

This is usually a sign that something is wrong. This symptom is commonly seen in fishes that have ich but, it can be a sign of almost any pathogen. 

Traces of chlorine, ammonia, and nitrite or even a drop or spike in pH can cause your goldfish to flash as well.

6. Spasms: 

When goldfish are irritated severely, they jerk spasmodically. 

This includes them shaking their head all of a sudden from side to side, flicking their fins, convulsion in their entire bodies, etc. 

One of the root causes of this problem includes problems with the quality of water. In some cases, the parasitic infestation may also be the cause of irritation.

7. Clamped Fins: 

There are two reasons why goldfish clamp their fins:
Problems with the quality of water

Goldfish that have these issues swim will all fins folded in closely to their body as they move which makes them look like they are in a straight jacket. 

Some fish even twitch or flick their fins in an irritated manner. 

Just like flashing, clamped fins are a sign of discomfort and the causes include high amounts of nitrate or ammonia in the water. 

These fins are often accompanied by parasitic infections and they symptoms for this include flukes, ich, fish lice, and velvet include clamped fins.

This is why it is always important to test the water before you try to identify a disease.

8. Rapid Breathing: 

If you closely observe the patterns of your fish’s gill movements, you can quickly identify breathing problems.

If your goldfish is breathing fast, it may be suffering from the lack of oxygen.

If you keep your goldfish in a bowl (which is not at all recommended) chances are that insufficient water volume and no water agitation will make it difficult for your goldfish to breathe. 

So, to get to the sufficient oxygen levels, the fish breathes hard. If this is a case, you should move your goldfish to a bigger tank as soon as you can. 

If you fish is sitting at the bottom of the tank and breathing rapidly, it could mean that it is stressed.

Your goldfish can experience stress when moved to a new habitat (like your house) after a long car ride from the pet store. 

Sometimes, even the breeding season heightens the amount of stress a female goldfish experiences---this is probably because your female is exhausted after being chased around by males for hours. 

Another reason why your goldfish can be stressed is due to the poor conditions of water in the tank or disease.

You should always start by checking the water quality. If you find no problems with it, your fish could have parasite or gill flukes. 

Goldfish that experience difficulty in breathing clear their gills frequently by “yawning” repeatedly.

9. Swimming Upside Down:

Have you observed your goldfish having a problem in balancing itself in the water? 

If your goldfish is stuck upside down, chances are that she is having some problems with her swim bladder which is an organ in goldfish that controls the fish’ orientation in the water. 

One of the most common causes of goldfish flipping over is intestinal impaction. 

What does this mean?

Well, this simply means that the meals you’re giving to your goldfish may be too frequent or too large. This also happens if the meals consist only of one dish which causes an imbalance in nutrition. 

The best solution to combat this problem is to feed your fish some dethawed frozen peas.

However, in some cases, problems with buoyancy aren’t necessarily the symptoms of the flip-over disease or swim bladder disorder. 

Your goldfish can have trouble swimming if the water in the tank has high nitrates or if ammonia is present in the tank.

If a fish has internal parasites, it may lose its appetite and this may ultimately cause the fish to float or flip over.


If your goldfish tips slightly on to one side, it might be a normal behavior---this is true in case your fish doesn’t have a dorsal fin which will help the fish balance in the water---you may additionally notice that the fish looks thin. 

Water which is high in nitrates can also cause the symptoms.


The thing is that healthy goldfish eat everything they can and don’t leave anything behind. 

However, if your fish is eating everything eagerly but is spewing it back out again in a cloud of ground up pellets means that there’s a problem.

Sometimes, when fish are under stress, they can’t actually swallow their food. 

This is commonly seen in fish that were just brought home from the store. 

If that’s the case, your fish just needs some time to adjust to the new home. 

Other things that can cause the problem are mouth rot or a gill fluke infestation.

Other things include internal fluid buildup which makes the fish unable to swallow the food when they are at an advanced stage of the condition. 

In this, the goldfish eventually becomes too sick to even eat and euthanasia is your best option because starvation leads to a slow and painful death.

Common Physical Symptoms

Sometimes, goldfish can exhibit physical symptoms before behavioral ones. In this section of the blog, I have compiled a list of some common physical symptoms and explained what they could mean. 

Let’s take a look.


1. Bulging Eyes: 

If sacks filled with fluid surrounds your goldfish's eyes, or if they unnaturally protrude, it could be a sign that your fish has Pop-eye which is a bacterial infection. 

If your goldfish also has dropsy, pine-cone scales along with the bulges, then, it means that the condition is a terminal one and the best thing you can do is to euthanize your fish at this point. 

Some stunted goldfish also have permanent bulging eyes which is a result of disproportionate growth.

2. Cloudy Eyes: 

Do your goldfish’s eyes look foggy like frosted glass? 

Your fish may also have problems in seeing food and may even bump into different objects.

This symptom is known as Cloudy-eye and is caused due to bacterial infection which sets on after an injury, is a result of damage due to some sort of burn due to ammonia or any other strong chemicals in store bought medications.

3. Missing Or Damaged Eyes: 

It is common for goldfish to incur some damage to the eye. 

This could be due to running into a sharp tank decoration, mishandling, infection, injury from another fish in the tank, or chemical burns from water toxicity.

In some fish, the eye comes completely off which leaves the fish blind.

The goldfish variety most prone to eye damage or eye loss is the telescope eye goldfish. This is because their eye stems protrude a lot and their size. 

The good thing is that most goldfish heal on their own afterward.


1. Red Gills: 

Sometimes, goldfish owners are concerned when they notice the red color inside the fish’s gills. This isn’t usually something you need to be concerned about. You can easily see the red in the gill covers on matte and white goldfish. 

If your fish has swollen and stuck open gills, bacterial gill infections or gill fluke could be the cause. Like all parasites, you can treat gill flukes with salt.

2. Pale Gills: 

Healthy goldfish should have gills that are vibrant red in color. If your goldfish has whitish or pale gills, it is a sign of illness---the most common being parasitic infections which include gill flukes which also causes the microscopic bleeding of gills which leads to loss of color.

3. Holes In Gill Covers: 

Holes in the goll covers are a sign of a severe bacterial infection. Your fish will need some antibiotic injections but, the holes are most likely to stay open even after treatment.


1. Mouth Stuck open: 

In some cases, goldfish get a piece of gravel lodged in its mouth while it is foraging for food at the bottom of the tank.

Usually, goldfish can work the gravel out on its own within a few hours to a day. 

So, it isn’t unusual for the fish to swim around with its mouth in the ‘out’ position. 

However, if it has been over 24 hours and there isn’t any improvement in your fish’s condition, you will need to extract the gravel.

To do this, you will need to gently hold your goldfish in one hand with tweezers in the other.

Slowly press down underneath you fish’s chin and use the tweezers to remove the gravel delicately. 

In some rare cases, the goldfish’s mouth is stuck open without any gravel in it.

Usually, the mouth snaps back into place on its own but returns to the stuck position every time the fish opens it.

This is rarely seen but people speculate that it is due to stunted and disproportionate growth if the fish has been kept in too small of a tank for too long.

In this case, the fish cannot eat and will face death unless euthanized.

2. Mouth Opening To One Side only: 

This isn’t really a problem with the water in the tank or symptom of a disease, it is a genetic defect which causes the fish to have a small mouth which is angled to one side or inverted. 

If your goldfish has this condition, it may need to have its food served in smaller pieces than others to eat properly.

3. Red Mouth: 

In some cases, goldfish have a red and inflamed mouth, it may even begin to cave in on itself.

In this case, the goldfish has mouth rot. The fish may rub its mouth on decorations and tank walls which causes further irritation. 

Blisters also commonly form. Mouth rot needs immediate attention because it can get easily out of control.


1. Black Spots: 

Changes to the natural pigmentation can cause your goldfish to develop black spots on the head, scales, or even fins. This can also happen if your fish is healing from a recent injury. 

With age, goldfish change color in unexpected ways. 

However, black marks that seem to come and go in a cycle should be a cause of concern as they can be a sign of a recurring issue with a bullying companion or tank water. 

Ammonia burns heal black but usually revert to the original color with time if the water remains stable. Fins that are healing after fin rot may also have black edges.

2. White Spots: 

If your fish has white spots on the body, chances are that it’s suffering from ich.

These protozoa are like white specks of lint which multiply until both the fins and the complete body of the fish looks like it has been sprinkled with salt. 

In some cases, a single speck of ich will probably come and go, and will affix itself to the wen or the tail of your goldfish when the immune system has been compromised.

3. Raised Lumps: 

If you observe abnormal lumps underneath your goldfish’s skin or scales, they most probably are tumors which may either be cancerous or not.

Tumors come in all sizes, colors, and shapes and can get big if left untreated. 

They may look like a dark lump, brown lump, white lump or even pink lump. 

Tumors may show up on your fish’s fins as a result of toxins building up in the water.

They are removable, but can cause death if left untreated.

4. Red Spots On Body: 

The red spots on a fish’s body are most probably ulcers. These start out as tiny red patches of collected blood on the skin and grow until the fish’s skin starts to swell and erode. 

Red spots may also be bites from parasitics such as fish lice, anchor worm, etc.

5. White, Milky Film On Body: 

In this case, the slime coat of goldfish is hyperactive and produces excess mucus which is usually in response to the poor environmental conditions or threat of parasites.

You should check the pH for fluctuations and test the water to check whether or not nitrite or ammonia is present. 

A parasitic attack is the most probable cause if the water is fine. Parasites such as anchor worm and skin flukes cause the goldfish to produce a milky coating on the skin

6. Pale color: 

If your goldfish look paler than normal, it is a sign that your fish isn’t doing too well and has a disease or the quality of water is rather poor. 

If you detect nitrates in the water, that’s what’s causing the pale appearance. 

You should start by changing 50% of the water immediately if ammonia or nitrite levels show up, or if the pH has suddenly shifted. 

Stress is another probable cause for the lack of color over a period of time. You should remove the source of stress---like an aggressive tank mate to reduce stress. Goldfish also change color when they’re battling a disease.

7. Sores: 

If you see painful-looking red sores or ulcers on your dish’s body, chances are that they’re caused due to a bacterial attack on the skin when the fish’s immune system is suppressed due to water quality. 

Ulcers can continue to eat away at your goldfish’s skin until the it can take no more and finally dies.

8. Fluffy Patches: 

If your fish has cotton-like growths, they are most probably caused due to bacterial or fungal infections. You can see the fluffy patches on the fish’s body, head, and even the fins.

9. Worms Sticking Out Of Body: 

These anchor worms are basically parasites that attack the goldfish during certain seasons in a year. They are easy to treat if you catch them soon enough.


1. Red Belly: 

The most probable cause of a red belly on a goldfish is due to nitrite poisoning.

This is usually due to poor water quality. At an advanced stage, this can even cause death or internal bleeding. 

Goldfish with this symptom are already at an advanced stage and should be euthanasia because they die a slow death otherwise. 

You should change the water to save the other fish in the tank.

2. Swollen Belly (Bulging Abdomen): 

If your goldfish has an unnaturally bulging stomach, egg impaction is the most probable cause, If a female goldfish has impacted eggs, it is more prone to getting bacterial infections with time. 

The only way you can save your fish is by using a hand-spawning-like method which helps release the egg. 

In case the goldfish aren’t mature enough to bear eggs, they may have a liver or kidney disorder which can only be fixed through surgery.

3. Sunken Belly (Abnormally thin / Wasting Away): 

If your goldfish has a sunken belly, chances are that it is suffering from the side effects of having ammonia accumulated in its tank.

This means that the fish is more prone to getting bacterial infections, which can make its stomach appear concave. 

If there are no problems with the water, chances are that the goldfish is attacked by flukes or other parasites that cause the goldfish to lose its nutrients.

4. Bent Back: 

This means scoliosis in fish which is an incurable condition that is caused due to electrocution or genetics. This may even cause your fish’s scales to pinecone at the curve of the spine.


1. Scales Sticking Out All Over: 

The most probable cause is dropsy which is a condition in which fluids buildup in the goldfish that cause its body to swell up in such a way as to make the scales stand out and prickle.

Dropsy isn’t a disease but is a sign that something is seriously wrong with the quality of water or the fish’s internal organs. When combined with bulging eyes, dropsy is terminal.

2. Scales Peeling: 

If your goldfish’s scales seem to have peeled back in a patch or an area, leaving a part of the fish’s body bare, it is called a burn.

They are caused due to the fluctuating levels of pH which usually occur while the tank is still cycling and trying to establish a colony of beneficial bacteria.

3. Scales Coming Off / Missing: 

If your goldfish has missing scales, it means that there is an area on your fish’s body of the metallic scaled goldfish that doesn’t reflect any light and appears darker than the rest of the scales.

This could be due to flashing.

Tail & Fins

1. Bloody Streakes / Red Spots in Tail Or Fins: 

This means that there is a problem with the water and it has high levels of nitrites or ammonia which can cause the blood vessels to break or hemorrhage the veins in the goldfish’s tail.

This can cause red spots or lines of blood appearing in the fins. 

For recovery, you need to change the water regularly and ensure that there is proper room in the tank .

2. Shredded Or Frayed Tail Or Fins: 

If the tank has traceable amounts of nitrate and ammonia, it can cause the goldfish’s fins to fray and shred which looks like someone clipped them using a pair of scissors for the ribs of the fin to have a spiky appearance.

This is also caused due to fin rot. Hexamita, a parasite brought on by poor environmental conditions, can also cause this condition.

3. Tears In Tail Or Fins

If you have multiple goldfish in the tank, the aggressors may split the victim’s fins. Bullies usually grab the victim’s tails and cause splits to appear in it.

4. Milky Film On Tails Or Fins: 

The main cause of milky film is the excess mucus production which usually is a response to either poor environmental conditions or a parasitic attack.

You can detect milky skin on the Black Moor goldfish quite easily.



This occurs if your goldfish’s diet isn’t varied enough and the air bubbles from same meal accumulate in the fish’s digestive tract and get expelled.

Healthy stool has the color of the food---which is dark brown and it should sink at the bottom.


Stringy and hollow poop which is long and trailing means that your goldfish has internal problems such as a poor diet or an intestinal bacterial infection. 

4. The possible causes Of The Things Mentioned can be one of several things. See below...

Types of Illness and Diseases in Goldfish

There are numerous ailments, illnesses and disease that happen with goldfish.

  • Fin Rot (infection) - CONTAGIOUS TO OTHER FISH
  • Swim Bladder (floating problem)
  • Velvet (slimey granules) - HIGHLY CONTAGIOUS TO OTHER FISH
  • Anchor Worm (green hairlike parasites on fish) - HIGHLY CONTAGIOUS TO OTHER FISH
  • Fish Lice (round green/brown parasites on fish) - CONTAGIOUS TO OTHER FISH

Ich - Highly Contagious to Other Fish

This disease is very common in goldfish and generally happens to new fish. The stress of the car ride home and being introduced to a new habitat causes it to be more prone to disease.

Other stresses such as a drastic change in water temperature or maintenance of tank can affect your fish as well. The best thing to remember is to do all that you can to relieve undue stress on your goldfish.


  • Ich parasites are found in water that fish are in. It is many times unavoidable when introducing your new goldfish into your aquarium or tank that residual water from the original tank it was previously in will find its way into your tank.
  • After you have introduced new goldfish into your tank, be vigilant in testing the water to maintain good water quality.


  • Small granules on fish that appears to be like salt grains
  • goldfish are breathing heavily
  • goldfish rubs up against the wall of the tank or other objects in the tank


  • Before treating, slowly warm the water temperature to 75-80 degrees F. The increasing warmth will cause the parasites to detach from the fish.
  • Remove plants from the tank. Treatment will damage and even kill plants.
  • Do a twenty-five percent water change. Test water to ensure all levels are optimum.
  • Add aquarium salt (.03% concentration): one teaspoon for every gallon of tank water.
  • Over the next twenty-four hours, repeat steps 1-4 every twelve hours (total of 3 times.)
  • Allow the aquarium salt to remain in the tank water for two weeks. After that do a 50-75% water change.

Problems with Buoyancy

There are several causes when your goldfish cannot float correctly. If your fish is floating upside down, swimming sideways or appears to be bloated, it’s best to narrow down the cause and then treat accordingly.


  • Overfed
  • Poor Diet
  • Constipation
  • Flatulence
  • Swim Bladder Disease


  • Swimming sideways
  • Swimming upside down
  • Looks enlarged or swollen


For Constipation

  • Cooked peas help relieve constipation. Cooking the peas makes them soft. Make sure to remove the outer peel. Don’t feed more than 1-2 peas per day.

For Swim Bladder

  • Clean the tank to lower levels of bacteria.
  • Raise water temp to 70-80 degrees Fahrenheit.
  • Let fish fast for three days. Monitor to see if fish improve.
  • If symptoms persist, get an antibiotic from pet supply store.

Fin / Tail Rot - Contagious to Other Fish                                                    

Fin Rot and Tail Rot in goldfish are apparent when you notice your fish’s fins or tail appear as if they are frayed or torn. If treated promptly the tissue can grow back, however, if the rot is in the immediate area of the body, it will not grow back and can even enter the body of the fish which is fatal.


  • Stress
  • Poor water quality
  • Overcrowding (too many fish)
  • Sudden water temperature change


  • Fin / Tail appear frayed, torn or ragged
  • Edges of fin / tail become white from bacteria eating away


  • Remove sick fish from the tank and place in a separate container.
  • Using a fresh, clean fishnet, remove all other fish from tank and place in a separate container (do not put them in with sick fish). Fin Rot is contagious, so make sure you do not use the same fishnet that you handled the sick fish with.
  • Thoroughly wash (using hot water, no soap) and clean tank as well as all tank decor.
  • Wash gravel
  • Do a water change: 100% using conditioned water.
  • Use new tank water to rinse the filter. Place filter into the tank.
  • Check pH levels before placing healthy fish back in.
  • Slowly add all fish back into the water.
  • Monitor the sick fish for a few days and if it does not improve, add a fin rot treatment (you can purchase at a pet store.)

Fungal Infection -  Highly Contagious to Other Fish                           

Fungal infection is contagious to the other fish in the tank. If not treated quickly, you can end up losing your fish. This infection can become a secondary condition of goldfish  that have already been sick from something else.


  • Stress
  • Lowered immune system
  • Poor water quality


  • White growths on body and fins


  • Because this is highly contagious, the sick fish need to be removed from the tank and placed into a hospital tank.
  • Purchase a fungal treatment at your local pet store.
  • Treat your sick fish (in the hospital tank) with the fungal treatment.
  • Monitor the sick fish for a few days and if no improvement, do a salt bath treatment.
  • When your sick fish has healed, transfer it back to the main tank.

Velvet Disease -  Highly Contagious to Other Fish

Velvet disease is parasites that resembles small dust particles on the fish. It generally begins to develop on the spinal area of the fish, and because the parasites are so tiny, it’s difficult to see.


  • Usually brought into tank water by new fish
  • Stress caused by poor water quality


  • Film (pale yellow color) develops on fish
  • Fish rubs against tank wall or other surfaces
  • Clamped fins
  • Heavy breathing
  • Weight loss


  • You can treat with a medication called formalin (available at a local pet store.)
  • Use caution if treating with formalin. It can easily burn your fish’s fins.

Anchor Worm -  Highly Contagious to Other Fish

Common among goldfish, Anchor Worm is not a worm, but a disease that is caused by a parasite.


  • New fish introduced to a tank may be carrying Anchor Worm which is contagious to the other fish.


  • Green-like hairs attached to fish. Areas of attachment are red and inflamed.
  • Rubs up against tank walls or other surfaces.


  • You will need to purchase a medication (Dipterex 98%) at your local pet store.
  • Follow dosing instructions carefully.

Fish Lice -  Contagious to Other Fish

Fish lice are parasites that are common in ponds, however, it can reach a fish tank.


  • New fish introduced to tank or pond may be carrying the lice which is contagious to the other fish.


  • Disc looking parasites that are dark olive color. Usually attaches to stomach, throat and fin bases on fish.
  • Rubs up against walls or other surfaces


  • You will need to purchase a medication (Dipterex 98%) at your local pet store.
  • Follow dosing instructions carefully.


This disease is very distinct in making the fish have a pine cone appearance. Unfortunately, by the time the fish presents with this appearance, it’s untreatable.

This disease is painful and you may find that making the choice to euthanize your fish is the best humane thing to do.


  • Kidney dysfunction (renal failure) causing fluid buildup
  • For older fish, prolonged exposure to low temperatures
  • Bacterial in kidney
  • Parasites in kidney


  • Bloating
  • Pinecone appearance from fluid retention pushing scales outward
  • Eyes distended from the socket
  • Body or fins develop redness


  • You will need to purchase medication for treatment at your local pet store.
  • Following dosing directions closely

Hospital Tank

Make sure before treating your fish, you assess the water quality and checked your filtration system.

The hospital tank needs to be separate from your regular fish tank and is to be used only for quarantining new fish, separating sick fish from healthy fish and for treatment of sick fish.

Image result for hospital goldfish tank

How do I set up a Hospital Tank

  1. Set up a separate tank with a filter system. Include plastic plants, rocks, etc. to provide hiding places for the fish (this helps calms the sick fish.)
  1. DO NOT place any substrate in the hospital tank on the floor of the tank. Loose food gets caught in it causing water quality to decline rapidly.
  1. Transfer some of the established bio media from the filter in the main tank into the hospital tank. By doing this, you introduce the media to the hospital tank that will help to maintain the nitrogen cycle.
  1. Set the filter on the lowest setting. This will ensure that the movement in the water is at a minimum. Rapidly moving water can add stress to the already sick fish.
  1. Using a mesh bag, place some of the main tank’s substrate into a bag and put directly in the hospital tank.
  1. Turn on the heater to reach ideal water temperature.
  1. Transfer sick fish over to hospital tank using a net (not your hand.)
  1. Proceed to treat sick fish in the hospital tank.

Final Words: Your Ultimate Guide To Goldfish Diseases and Symptoms

I hope that I was able to go through everything in this blog post.

Most of the symptoms are caused due to poor tank conditions. So, you should always make it a point to check the tank before you diagnose your fish.

In most cases, better environmental conditions mean easy recovery. 

Being vigilant in maintaining water quality in your tank not only keeps your goldfish happy, but healthy!