My Fish are Sick, What do I do?

My Fish are Sick, What do I do

Most recent update; 12-14-2021

The purpose of this article is to provide basic answers to the most common questions asked about treating and preventing fish diseases or related issues in Aquariums.
Unlike other articles on this website written in FAQ format, in this article we will ask the questions, followed by important “Blanks” to fill in by the reader.

These Questions will be in the generally best order of importance to resolving the problem

Much of this information is courtesy of:
“Aquarium Disease Prevention”
“Aquarium Medication Use”
Please see the above articles for much more accurate and in depth information.

Suggested Further Reading from Fish Beginner:
What makes a healthy aquarium or unhealthy?

Strongly Recommended Further Outside Reading Before Starting ANY Treatment:
Fish Diseases | How to Treat Sick Fish


  • What is the effect of water parameters on your fish or other aquatic inhabitants?

    These are very important for treatment and prevention of fish diseases as often it is the water itself that caused the illness.
    As an example, an ammonia reading of 4 ppm is going to lead to a fish that is sick with torn and disintegrating, red or bleeding gills, & more. Secondary bacterial infections often result.

    The point here is all the medications in the world will not solve this problem until the ammonia levels are returned to normal (& even then the damage may have been so severe a complete recovery is not possible).
    As well, even low levels of ammonia or other parameters just slightly less than optimal will slow a recovery with treatment.
    So the bottom line is FIRST MAKE YOUR WATER PARAMETERS NEAR PERFECT if possible, and this includes Mineral Cations, GH, & KH (& even rH is possible)

  • What are your water parameters?

    Know these parameters:

    • Ammonia and/or Nitrites;
      These should be as close to 0 as possible, if these were recently higher, this could have been the cause of an sick fish issue
    • pH;
      Make sure pH is stable and not fluctuating. If a fish that was recently added is now sick, a sudden pH change and subsequent shock is one possibility.
      See: Fish Acclimation
    • KH;
      As a generalization, make sure you maintain a KH of 80 ppm or higher and make sure you maintain a KH number that is stable (chart your KH)
      If KH is suddenly dropping, look for high amounts of waste accumulation, over feeding, etc and REMOVE it
    • GH [Including Mineral Cations and Osmoregulation];
      While old school aquarium keepers without a knowledge of the importance of aquarium electrolyte/mineral ion chemistry may warn against a high GH; the FACTS are a GH of maybe 500+ MAY be a problem, but most often the true problem is a GH under 150 ppm or a GH that is negatively charged (depleted of positive mineral ions) is much more likely the problem.

      The bottom line is if you are having disease issues, one aspect to improve is the constant addition of positive mineral ions of which GH is the carrier.
      Improve this by water changes, aquarium mineral blocks, oolitic sand in a filter media or other related aquarium keeping practices. Mineral blocks that slowly dissolve such as AAP Medicated and Regular Wonder Shells are your best bet for this.
      Without adequate aquarium Redox balance and related fish osmoregulation; fish appetites will suffer, and treatments will often fail.

      The BEST resource for aquarium mineral blocks: AAP Wonder Shells; Aquarium Mineral Blocks (Only fresh, not clearance as with Amazon & other discounters, which is important as Wonder Shells lose their mineral Cations over time)

      See: Aquarium Chemistry; In Depth
      OR Aquarium Redox

      This video helps demonstrate how mineral Cations remove oxidizers (including chlorine):
      AAP Wonder Shell, Oxidizers, chlorine, Aquarium Co-op
      VIDEO: Aquarium Redox Part 2 | Oxidizers & Reducers | AAP Wonder Shell Experiment

    • rH [relative hydrogen];
      While not as well known and usually not something the average aquarium keeper can test for, since besides an accurate pH tester, it requires an expensive Redox meter; this is still a real and important parameter that at least an advanced fish keeper should consider.
      When this parameter is out of balance, this can result in oxidative stress that can shorten lifespan over time and make fish more susceptible to disease both directly and indirectly. Often in the end, a weak fish that shows signs of many possible diseases, but no one clear diseas can trace back to a poor Redox Balance and poor rH score
      The end result to may make treating a sick fish more difficult even when correct medications are utilized.

      More about rH; Aquarium Redox; rH

      For beginning fish keepers, simply following procedures that will likely keep a rH reading between 23 & 26 would be suggested [this includes constant mineralization, lowering bio load, good filtration/sterilization/circulation, etc.].
      Correct Aquarium Redox Maintenance: Redox as it pertains to Aquarium; Maintenance

  • What should I look for on the fish?
    My fish are sick, symptoms*Torn or ragged fins
    *Red Gills
    *Unusually lethargic behavior
    *Gasping at surface
    *Rapid respiration (“breathing”)
    *White salt like spots
    *Velvet like sheen, fine dust like appearance
    *Sores, Ulcers, OR sores that continue to grow
    *Bloody streaks on the fins, tail and body of the fish
    *Small Sores, that spread often with white threads inside the sore
    *Fuzzy large white spots
    *A white to grey cottony growth
    *Small worms on glass and/or wiggling in the water
    *Loose feces (similar to diarrhea), or white (Mucous covered) feces
    *Flesh eating away
    *Pop eye
    *Eye Infections
    *Sudden, Un-explained Fish Deaths
    *Slow wasting away, often over months
  • What medications should I always have on hand?
    My fish are sick, medications to keep on handThis list is based on professional aquarium maintenance persons generalized use and what they consider a must in their “house call” kits. This list includes a link to a reputable seller who has been professionally using and selling these products since the 1970s.
    This list is FAR from complete, as often other medications are called for, especially in difficult or rare diseases.

    *Methylene Blue from AAP OR BETTER, Premium MethyBlu from AAP (Methylene Blue); for Fish Baths, swabs
    *Potassium Permanganate from AAP; also for fish baths, swabs
    *AAP Wound Control (Merbromin); A must have for external sores/ulcers both from injury or Aeromonas infections
    *AAP Super Ich Plus (STRONGEST), AAP ParaGuard, Rid Ich (Brand Names) or similar malachite green, formaldehyde based formulas
    *AAP Nitrofuracin Green; Synergistic Nitrofurazone, Sulfathiazole Sodium, & Methylene Blue Full Spectrum Treatment; Good for newly arrived fish in quarantine situations.
    Also good for healing wounds and ammonia burn on newly arriving fish. Works well for sores on fish in Koi ponds.
    Anti- microbial, anti- protozoan, anti-bacterial, anti-fungal. Wide spectrum

    *Kanamycin; For many gram negative infections such as Columnaris, although it MUST be combined with Nitrofurazone to be effective for Columnaris, but still inferior to the already blended Spectrogram.
    *AAP Yellow Powder (premium Nitrofurazone & Acriflavin); for many gram negative infections such as Aeromonas & Columnaris (probably the best treatment for Columnaris, especially when combined with Kanamycin)
    *AAP Metronidazole; excellent for intestinal parasites and many intestinal bacterial infections as well. Some effectiveness for external parasites and gram positive infections.
    *AAP Myacin; Superior Erythromycin Phosphate Treatment (much better than standard API Erythromycin sulfate! A good choice for many eye infections and the occasional less common gram positive aquatic infection
    *AAP Medicated Wonder Shell (Brand name); these are excellent preventative and even treatment especially for Velvet and sometime fungus. This is a fair/good treatment when identification is difficult, especially when water mineral ions/electrolytes are low. These are also an excellent follow up to stronger treatments such as AAP Super Ich Plus for Ich.
    Medicated Wonder Shells are also useful as an important part of many treatments including internal parasites, swim bladder issues [especially with many Betta issues].

    *AAP Sulfaplex (Sulfathiazole); another good catch all for mild to moderate bacterial infections as well as an excellent addition to Ich treatments in sensitive fish such as Clown Loaches.
    *Res-Q; Medicated slime coat water conditioner, great for minor injuryies, new fish introduction
    *AAP Shieldex AND/OR StressGuard from AAP; Shieldex, along with StressGuard are the premium slime coat protection stimulation products.
    StressGuard is useful to reduce stress and ammonia toxicity whenever handling or transporting fish, while Shieldex not only stimulates slime coat protection, it also immediately adds this slime coat and is also an aid for nitrifying bacteria

    *Melafix and Pimafix from AAP (Brand Names); for minor fish issues (such as a minor injury), basically used as you would Neosporin in humans. In other words NOT for serious issues.

  • What should I treat with?

    Assuming correct/corrected water parameters, the next consideration is a Fish Bath, Dip, and/or Swab if possible (by if possible, I mean a fish that can reasonably be handled in a 1 quart to 1 gallon bath container, not a 15 inch Pacu!).
    Since the purpose of this article is not to go into detail, I would suggest this easy to understand and in depth article on this subject:
    Fish Baths, Dips, Swabs.

    Before treating, most chemical adsorbents such as carbon should be removed to prevent the removal of medications required to treat. Also small 10-20% simple water changes are suggested to lower organics in the water column that will also remove medications (water changes can also remove toxins produced by some medications, which is why changing water prior to subsequent treatment is also a good idea.

    Next I will go into the previously listed symptoms and then provide some possible suggestions albeit not complete suggestions.
    Is is important to note that this article is NOT intended as a diagnosis chart, nor do we recommend one.
    Our intention here is to provide suggestions as to the problem and have the reader of this article read further in depth articles as to how to identify, treat, and prevent.

    *Torn or ragged fins
    This can simply be from other fish attacks or other injuries, or mild bacterial infections such as Pseudomonas.
    Watch your aquarium and separate fish if it is an injury from other fish.

    Often a good preventative treatment for long finned fish such as Betta or Guppies when introducing new fish or after injury is “AAP Bettamax”. This also treats the pathogens in most mild to moderate fin/tail infections.
    Resource: AAP Bettamax (Nitrofurazone, Methylene Blue, PVP, Vitamins, NaCl, Sulfas: methazine, diazine, and merazine Combination)

    Be aware that an internet myth started in blogs a decade ago has lately spread to social media and that is of stress related “Betta tail biting”. Those supporting this myth have not used any basics of scientific method and fail to recognize the importance of mentoring with a problem decades ago discredited by professionals.
    If you have a Betta, please read the next reference and follow the tips for the possible causes before just assuming this myth while real issues continue to cause issues that will allow this to go unchecked.

    Please Read these articles for further treatment information (of course considering a bath first or maybe as the only treatment):
    Fin and Tail Rot in Bettas and other Fish
    Aeromnonas Infections
    Common Aquarium Myths; Betta Tail Biting

    *Red Gills
    This is often caused by high ammonia and/or nitrites. Lowering these to safe levels will go a long way in affecting a cure.
    A Fish bath in Methylene Blue is also called for.

    This can also be a symptom of gill parasites (such as Flukes) or occasionally Aeromonas.
    #Aquarium Parasites
    #Aeromnonas Infections

    *Unusually lethargic behavior
    This can be due to an aquarium that is too cold, so look into this.
    It can also be a stressed fish due to other fish harassment or poor water parameters (low positive mineral ions/electrolytes are common cause, see Aquarium Chemistry).
    If a fish is missing minerals such as calcium, magnesium, & others; it cannot carry on with normal osmotic function. This can result in inability to fend off many disease pathogens or sometimes even digest food properly.

    Lethargic behavior is a possible symptom of many diseases, so it is important to look for other symptoms to refine the possible issue.

    *Gasping at surface
    This can be due to lack of oxygen, high ammonia/nitrites, Flukes, Velvet, Oodinium (saltwater), and occasionally Ich.
    As well, incorrect application of CO2 in planted aquariums (generally at night) can also results in gasping at the surface and unfortunately sudden fish die offs.

    See these articles:
    #Planted Aquarium Care; Use of CO2
    #Aquarium Parasites

    *Rapid respiration (“breathing”)
    Similar to the above description, although I would generally exclude lack of oxygen if the fish is not at the surface.
    I would then add the possibility of harassment by other fish and pH shock from sudden pH changes, often when fish are incorrectly introduced.

    See: Disease Prevention; Fish Acclimation

    *White salt/sugar like spots
    White spots the size of a large grain of salt or sugar is a common symptom of Ich/Ick (Ichthyophthirius Multifilis in freshwater and Cryptocaryon Irritans in saltwater).
    These spots often are first visible on fins. Flashing or scratching on rocks is sometimes a symptom too.

    For much more about this disease, treatment and prevention, see:
    Aquarium Ich: Ichthyophthirius Multifilis and Cryptocaryon Irritans

    *Velvet like sheen, fine dust like appearance
    A velvet or fine powder sugar like fine dusting on fish can be a symptom of freshwater velvet or in saltwater fish; oodinium.
    Sadly, oodinium in saltwater fish is relatively and very difficult to treat once the tank is infected, so prevention is key. With freshwater velvet, this is less common and not as difficult to treat.
    Please read these articles for much more in depth explanation of these infestations:
    As well as the good acclimation procedures are VERY important for prevention, see:
    #Disease Prevention; Fish Acclimation

    *Sores, Ulcers, OR sores that continue to grow
    These can start with injuries and/or can be caused directly by bacterial pathogens such as Columnaris or Aeromonas.
    Aeromonas is generally more common where water conditions are less than optimum while stress is often a common factor with Columnaris. Both can be the result of a secondary infection.
    Sores and Ulcers should be treated with Fish Baths, Dips, and/or Swabs along with appropriate in tank/hospital tank treatments (if necessary).

    Please read these articles for more:
    #Aeromnonas Infections
    #Columnaris Infections Infections
    #Fish Baths, Dips, Swabs

    *Bloody Streaks on the fins, tail and body of the fish
    This is Septicemia, sometimes identified as the Internet invented disease, “Red Pest”.
    Either way whether you use the correct medical terminology or the internet nickname, this is a symptom of other diseases, NOT a disease of its own.

    The usual cause is an internal infection of Aeromonas Bacterium that has gotten into the bloodstream. Occasionally some internal nematodes (a phylum of worms) can cause these symptoms.
    Treatment as per an internal infection of Aeromonas, including the often root causes of Aeromonas is essential to effect an often difficult cure.

    This includes a fish bath with Kanamycin possibly with Neomycin or Metronidazole.
    Soaking fish food with Neomycin and/or Metronidazole prior to feeding is also helpful.

    For further information, please read and follow ALL the instructions in these articles:
    #Aeromnonas Infections
    #Food Delivery of Fish Medications
    #Aquarium, Fish Parasites, Worms; Nematodes
    #Red Pest, Invented Fish Disease, Actually Septicemia

    *Small Sores, that spread often with white threads inside the sore
    This may be Anchor Worms, especially with goldfish. In fact even more common when the goldfish or other tank mates are new (within 2-4 weeks).

    A swab using AAP Wound Control (Merbromin) OR Potassium Permanganate (diluted 50% with water).
    The followed by Fish Baths with Nitrofurazone by AAP, Methylene Blue by AAP, and Metronidazole OR AAP Bettamax (Bettamax combines many of these ingredients and can be used at double dose in a fish bath)
    Best if possible, is using tweezers to pull out the worm then swabbing with Methylene Blue or Hydrogen Peroxide.

    An “in-tank” treatment with Dylox is also suggested if fish present will tolerate this product.
    Resource: AAP Dyacide (Dylox)

    #Fish Parasites; Anchor Worms
    #Fish Baths, Dips, Swabs

    *Fuzzy large white spots
    This can be from Fungus (actually Saprolegnia).
    Or if this is a small white spot/wound that within a week, the white area increases to a larger strip in size, this could be Columnaris.

    Saprolegnia (Fungus) can result from decaying organic matter, especially in water with acid pH.
    Saprolegnia can result from a minor to major wound, and is relatively common with many lower substrate fish such as Cory Cats.

    Saprolegnia (Fungus) can also be the result of the “Raw Shrimp” cycling method, which should not be used, especially by amateur aquarium keepers.

    Products such as Pimafix or Triple Sulfa can work for mild cases.
    For mild to moderate cases, AAP PolyGuard can be effective.
    AAP Triple Sulfa can also be combined with Medicated Wonder Shells are another often effective alternative.
    For more serious cases, besides the above suggestions, direct application of AAP Wound Control (Merbromin) can help futher

    Please Read these articles for more treatment, prevention, & identification information:
    #Columnaris Infections Infections
    #Fungus, Saprolegnia
    #Raw Shrimp Aquarium Cycling

    *A white to grey cottony growth, Often on mouth or a “saddleback” type growth

    This is generally caused by Columnaris Bacterial infections.

    Please read this article for more:
    #Columnaris Infections Infections

    Columnaris in Fish VideoYouTube; How to: 4 Steps Columnaris Treatment Fish Bacterial Infection
    This video goes over the basics of the full four step plan of properly treating Columnaris in aquarium fish and is a compliment to a FULL reading of the above referenced article.

    *Small worms on glass and/or wiggling in the water
    These are Detritus Worms, NOT Planaria as so many websites and forums often misidentify.
    These worms eat organic waste and usually are not seen until their population explodes, usually due to spikes in waste. Treatment is not the answer, rather correcting the cause.

    Please Read these articles:
    #What are these small white worms in my aquarium?
    #Aquarium Planaria

    *Loose feces (similar to diarrhea), or white (Mucous covered) feces
    This can be caused by internal/intestinal nematodes (worms), or intestinal Aeromonas infections.

    Please read these articles:
    #Aquarium Parasites; Nematodes, Trematodes, Worms
    #Aeromnonas Infections

    *Flesh eating away
    This is often the result of virulent Columnaris infections.
    Treating for this type of infection often involves a “cocktail” of medications and perfect water conditions and fish baths/dips/swabs are a MUST!

    Please Read:
    #Columnaris Infections
    #Fish Baths, Dips, Swabs

    *Pop eye
    This can have many causes, one of the more common is Aeromonas bacterial infections.
    Water conditions and to a lesser extent Streptococcus bacterial infections can be the cause.

    Please Read:
    #Pop Eye Infections, Aeromonas
    #Streptococcus, Eye Infections in Fish
    #Fish Osmoregulation

    *Eye Infections
    Cloudy eyes and similar eye infections are often one of the more rare gram positive infections caused by Streptococcus. Sometimes Saprolegnia or Aeromonas can be the cause, but this is not too common.

    Please Read:
    Streptococcus, Eye Infections in Fish

    *Sudden, Un-explained Fish Deaths
    There can be many causes here that includes a sudden increase of ammonia or nitrites. What is also worthy of note is that “Toxic Ammonia (NH3) changes to ammonium under 6.0 and ammonium (non toxic NH4) switches back to toxic NH3 over 7.0”. This means if your pH increases after a water change or ceasing the use of CO2, especially in a planted aquarium, this can cause a sudden increase of ammonia (NH3). This can then convert back when CO2 is re-introduced thus lowering ammonia.

    Sudden un-explained deaths can also be caused by introduction of toxins on an aquarium keepers hands or objects/decorations. As well spraying toxic chemicals near an aquarium can also be such a cause.

    Further Reading:
    #Aquarium Nitrogen Cycle; Including Ammonium/Ammonia

    These are a few of the most common causes for this definition of fish death, with many possible causes.
    Neon Tetra Disease and similar sporozoan infections can quickly kill Tetras along with many other species

    Here is an expert source for Neon Tetra Disease, with practical experience:
    #Neon Tetra & FNT Disease; Sporozoan Fish Infection

    Beware of articles/videos that are violating the DMCA while Google looks the other way that have partly used information from the above article without permission and have no long term practical experience. This includes “The Spruce” and “Aquarium Co-op”

    Iridovirus can also be another cause of unexplained fish death

    *Slow wasting away, bone deterioration, often over months
    This is usually caused by Mycobacterium Tuberculosis bacteria, which is not a common infection, but when it does “strike”, it can be very expensive and difficult to treat.

    Occasionally curvature of the spine (from bone deterioration) is symptom of Tuberculosis in fish, but unless other symptoms are present, it likely is NOT fish Tuberculosis.
    In fact in many livebearers it more likely is a symptom of age or poor water mineralization (or both).
    Sometimes just improving the water quality as per minerals such as the use of a Wonder Shell and these symptoms will dissipate, especially with livebearers.
    Please Reference:
    #Aquarium Chemistry; Basic to Advanced
    #Recommended Wonder Shell Resource based on actual product use: AAP Wonder Shells

    Please Read:
    TB in Fish; Mycobacterium Tuberculosis

  • Are there any suggested follow up treatments?

    Water Changes are a very important follow up. Make sure the pH is similar to that of the aquarium or does not alter pH more than .5 (less is better).
    The use of Medicated Wonder Shells, 1/4 doses of ParaGuard or similar malachite green based products can be helpful for Ich, or fungal infections.
    Triple Sulfa can also be used as a follow up for many bacterial or secondary infections following Ich outbreaks.

    However, most importantly maintain optimum water conditions and preventative measures such as level one UV Sterilization. Be aware that many UV Sterilizers now sold can ONLY provide clarification properties, NOT level 1 Sterilization (examples are the Green Killing Machine & AquaTop).
    #UV Sterilizer Use, Facts & Information
    #UV Sterilizer Reviews

#AAP Professional Treatments; Widest Variety of Treatments ANYWHERE
#SeaChem Products

#Columnaris in Fish, Bettas; What is Correct?
#Aquarium Canister Filter Troubleshooting
#Wonder Shells; Aquarium Forum Hall of Shame
#Algone Nitrate Controller
#Aquarium Planaria or Detritus Worms; Internet Miss-Information

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