5 Common Aquarium Fish Diseases and Their Cure 8

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One of the most tragic events that could happen to your aquarium is that your loveable tank mates could get sick and die of a disease that you were unaware of how to cure.

This post is here to help explain the top 5 most common aquarium fish diseases and how to fix them so you can keep your fish healthy, happy and allow them to have a long lifespan.

5 Common Fish Diseases Plus Prevention and Cure

1. Fin Rot

Fin Rot is one of the most frequent diseases in aquarium fish; it is also one of the most treatable and preventable diseases.

fin rot common fish disease(image source)

Symptoms: The fins will turn white, opaque, appear inflamed, fray and may even become blood streaked. If the fin erosion continues up to the base of the fin, the disease could become deadly.

Cause: Environmental; When the fish are unhealthy, stressed or fin damage has already occurred. Factors such as; overcrowding, fin nipping, poor water quality, and poor quality food can contribute to the cause of Fin Rot.

Treatment: You can use available anti-bacterial medicines, perform water changes and the addition of aquarium salt will help. The drugs Chloramphenicol, Oxytetracycline, and Tetracycline, are good choices to help cure Fin Rot.

Prevention: Check the pH levels and water temperature to make sure they are ideal for your fish. Maintain good water quality and perform regular tank maintenance and never overcrowd or overfeed your fish.

2. Swim Bladder Disorder

Swim Bladder Disorder is most commonly seen in Bettas and Goldfish but it can occur in any species of fish. When a fish has swim bladder disorder, the swim bladder does not function normally because of physical defects or disease. Issues that affect the swim bladder specifically contribute to Swim Bladder Disorder.

swim bladder disorder common fish diseases(image source)

Symptoms: You will start to see problems with the fish’s buoyancy, they may start to sink to the bottom, float upside down, appear to have a swollen belly and struggle with swimming and balance.

Cause: The most common causes are compression of the swim bladder from other organs being enlarged. I.e., an enlarged stomach from too much air or overeating. Less common causes include; having an enlarged liver, enlarged intestine, or enlarged kidneys. Bacteria or parasites as well as mechanical issues and birth defects can also cause Swim Bladder Disorder.

Treatment: Try skipping meals for 2-3 days, then feed your fish skinned peas. (more about the skin pea treatment here) Increase the water temperature and make it easy for the fish to reach the surface by lowering the water level. If your water temperatures are higher, it will aid in the digestion process and help to avoid constipation, which could also cause swim bladder problems.

Use a broad-spectrum antibiotic if required. More antibiotics available for swim bladder disease can be found here.

If fasting isn’t working, perhaps the problem is not from an enlarged stomach but from another enlarged organ or type of infection.

Prevention: In order to prevent Swim Bladder Disorder, keep your tank clean and perform scheduled water changes. Thaw and soak foods before feeding and definitely avoid overfeeding.

3. Body Flukes

Body Flukes consist of tiny worm-like parasites that get into the skin, gills, and other body parts of the fish. They are also known as Gill Flukes and Skin Flukes.

body flukes skin flukes gill flukes common fish diseases(image source)

Symptoms: You might notice your fish scratching against objects in the tank, layers of mucus or slime over the gills or body, lesions, small blood spots, rapid moving gills, chewed on fins or gills, red skin, discolored or pale fish or rapid respiration.

Your fish may show signs of lethargy, intermittent swimming, surface breathing or minimal movement.

Cause: Poor water conditions, overcrowding, incompatible tank mates and stress.

Treatment: A quick treatment with antibiotics is important or an outbreak could occur and affect the rest of your tank mates.

Treat the tank with Droncit (Praziquantel) at 2 ppm (2 Mg/L) or a malachite green-formalin combination until all eggs and flukes are gone. Flukes can be eliminated from fish (but not the tank), by short formalin, salt (3 %), or Ammonium Hydroxide baths. Some more common helpful treatments can be found here.

Prevention: In order to prevent Body Flukes, quarantine all new fish before putting them in your tank. Avoid using live food that may contain flukes.

4. Dropsy

Once a fish’s immune system has been compromised by stress, it can become susceptible to Dropsy. Dropsy is commonly present in aquarium habitats.

dropsy goldfish common diseases(image source)

Cause: Poor water quality, ammonia or nitrite spikes, drastic temperature changes, improper nutrition.

Symptoms: Swollen belly, body and abdomen, skin lesions, bulging eyes, pale gills, ulcers, lethargy, the fish may stop eating and hang near the bottom or gasp for air at the top of the tank and show signs of unbalanced swimming.

Treatment: Dropsy is difficult to cure, some tank hobbyists take to euthanization to prevent spreading the infection to the other healthy fish in the tank. If Dropsy is tackled early, it’s possible to save the fish.

Move the fish to a different tank, add 1 tsp. of salt per gallon, feed the fish high quality foods and treat with antibiotics. Keep tank clean for several weeks. A good antibiotic to use to treat Dropsy is Maracyn-Two.

Prevention: In order to prevent Dropsy you will need to maintain the proper environmental conditions in your tank. Don’t overcrowd your tank, keep the tank and filters clean, don’t overfeed your fish and perform regular water changes.

5. Ich

Also known as White Spot Disease; it’s a disease that most hobbyists will encounter. This disease is parasitic and it could be fatal to your fish if not taken care of quickly and properly.

fish ich common fish diseases(image source)

Symptoms: You will see white spots on the body of the fish.

Cause: A compromised immune system due to stress from overcrowding or other environmental factors like diet, water temperature, quality and incompatible tank inhabitants.

Treatment: Isolate the infected fish and use Ich medication. Perform daily water changes on the isolated fish. Slowly increase the temperature every few hours to a maximum of 86 degrees. Clean and vacuum the gravel and replace the water every day until the signs of Ich are gone. Add aquarium salt to the tank to assist in gill function. Replace all filters, plants, décor and add the recommended does of Ich treatment until the spots have disappeared.

Prevention: Purchase healthy fish, quarantine new fish, keep water parameters and environmental conditions stable.

Prevention is Key

Dealing with fish diseases isn’t fun, and we’re sure you don’t want to see your fish buddies suffer or go through stress. Prevention is key in order to make sure your tank mates lives are long and happy.

Remember to purchase fish that are free of all signs of stress and disease. When choosing a fish to purchase, take your time to make sure that the other fish in the tank are healthy.

It would be a good idea to even place all new fish in a quarantine tank for 2 weeks to make sure that your newly purchased fish isn’t going to bring new parasites and contaminate your existing tank.

If buying new plants, make sure they are clean before placing them into your new tank. Keep movement and handling to a minimum when purchasing new fish to reduce stress.

Avoid drastic water changes, keep the tank clean and water parameters stable. Feed your fish a healthy diet and don’t overcrowd your tank.

What's Your Experience?

Have you had some success and failures with these common fish diseases? We would love to hear your stories, share it with the community in the comments section below.

About Dennis Hanson

Dennis is an experienced aquarist with many years of knowledge and experience in keeping successful tanks. He also has no relations to the pop group Hanson.

8 thoughts on “5 Common Aquarium Fish Diseases and Their Cure

  1. Reply Jeniffer Dec 8,2014 1:13 pm

    Great Article!

  2. Reply John McCauley Dec 8,2014 3:21 pm

    I would like to offer a word of caution on the use of antibiotics. I used Triple Sulfa to treat fin rot. It worked and took care of the fin rot. But, the sulfa turned the water dark red, then yellow. I have done numerous water changes and use a UV light in the tank. I have also switched to a canister filter. The water is improving gradually, but it sure has presented a challenge.

  3. Reply Sylvia Smith Dec 8,2014 3:31 pm

    I am rearing 10 koi fry in 160 litre unheated filtered professional aquarium tank with the idea of introducing them to our outside koi pond sometime next Spring. They were 1.25″ long at the end of July and are now different sizes up to 4″. The building they are in is unheated but double glazed and insulated. The lowest temperature recorded is 6.2C – in July it was 16C. Water changes of 10
    Litres are given every two to four days and regular readings of the water taken. There is no ammonia and nitrite and the KH and PH are correct. The GH is checked less often. There are two filters and a strong bubbler. We intend to move the 5 largest fish into a 300 litre similar tank once we have finished making the base.
    My questions are these:-
    What is the lowest temperature that you would offer them food this winter and how much? They have bee getting half a teaspoon of No.4 Fry food and a good pinch of catfish pellets 5/6 days a week but I noticed when I hoovered out the bottom of the tank this morning that some food has been left. I do not want to starve them but I do not want to kill our little squad with kindness!

    My other question is what is the lowest temperature that we may move the larger ones when the new tank is ready. I do not want to stress the fish. Obviously we would balance temps. in each tank before hand and use the normal way of introducing new fish in floating plastic bag into a pond.
    I look forward to your reply
    Sylvia Smith

  4. Reply Fish lover Feb 5,2015 9:00 pm

    This is a helpful article but it still doesn’t solve my problem.

    There is a brownish allge on the bottom of my tank and it is spreading.

    Another thing is my fish are turning black and then when they are all black they get lopsided sink to the bottom swell up and die. The are not gold fish or anything else they are a sunset pallywag, and one other kind but they are still both a communtiy fish haven’t laid eggs or anything only get fed twice a day and not a lot.

    Again with this website I was able to get an idea

  5. Reply Umakant Jul 28,2016 8:24 am

    Since last three days I noticed that my fish is sinked at the bottom of aquarium tank and after few hour it get collapsed. As I touch it starts slow movement. Removed to other water tank for a day and could survive. But now again found collapsed with very very small movement. What can be the reason and how to cure. Please suggest.

  6. Reply Rick Gould Jan 28,2017 2:48 am

    I have a 200 gal. tank. I’ve had numerous problems in the past , but ich is the worse……. I got that problem as we speak . I trying salt this time and temp. Change . I have about 60 small fish in it like neons,black stripe tetras,and some other compatible fish and snails 1 algae eater. I just noticed it and started losing fish . Hope I got it early enough to save them . If any body has some advice for help, be more than glad to take advice.

  7. Reply dee Jun 7,2017 10:45 am

    When any of my fish are ailing I treat the water in the aquarium with an ozonator. Works miracles! Pathogens etc cannot survive in a high-oxygen environment.

  8. Reply Ren. Jun 12,2017 7:51 am

    I know how late I am, but I am just so overwhelmed right now that I no longer care. My Three-Ray Bristle Nosed Catfish (it’s a mouthful but that’s it’s species) is turning red and breathing quickly. I change the water often enough, not too often, and it has a good and balanced diet, but it’s suddenly doing this? Is it normal? The PH levels are fine and the ammonia levels aren’t high at all, and there is nothing in the tank that she could hurt herself on, and I have grown very fond and attached to her as she is my third fish. I may be a bit under informed in caring for this species of fish (she is my second one as I said, my others were goldfish which are still thriving, and a Betta fish who passed away recently after a year and a half, the only other pets I have had is my guinea pigs, which are literally sitting behind me as I type this). I just need an answer so I can calm down and go back to bed, as it is 2:50 in the morning.

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