Koivet.com Resources for Fish and Koi Diseases, Illness Symptoms, Diagnosis, Treatment and Cure

Youtube has provided me with an avenue to reach lots of people with valuable messages about fish health. Saving Koi, goldfish and tank / aquarium fish has been a "thing" for me for decades and I've made a name for myself that way. Which is a double-edged sword. (My Youtube Channel)

I like helping people? But not constantly. And folks need to learn on their own, a little, too. 

So when people call the office asking what to do about a sick fish, I made some online resources for this. 

The single, most important series of videos I've done is the "Twenty Steps of Fish Diseases Diagnosis and Treatment." which basically takes a struggling person with a sick fish, and talks them COMPREHENSIVELY through twenty assessments and along the way, they ALWAYS figure out what's wrong. 

Twenty videos on fish health and diseases, symptoms and cure: "My fish is sick, what should I do?" 

So the above is a great set of videos. Actually, even if there's no problem because in this, you will discover the twenty MOST IMPORTANT things affecting fish health. 

Then, a successful hobbyist will know all about "The Cycle" also known as the Nitrogen Cycle (See video). That's the natural process where fish waste is converted through a series of bacterial processes to reduce it to plant food. If any step in the nitrogen cycle is defective or for some reason there's a build up of nitrogen (There's a test) the fish will be sick. 

Here's the first compound in the cycle that hurts fish:   Ammonia

The second water quality parameter of extreme import:   Nitrite

Thirdly, accumulation of algae food "Nitrate" is eventually hazardous to Koi and fish. 

Finally, the conditions of acidity / alkalinity in the water are critical for some species of fish. In particular, the "PH" of the water is crucial. It's common to see the PH collapse in the system, especially with too-infrequent water changes – dropping two or three points over night and kill most if not all the fish. How to support pH with carbonates is discussed in this video, as well.  There's an easy test for pH that is well worth having. 

For those of you trying to find test kits, foods, nets, medicines and other things recommended in my web sites and videos, please check out http://koivet.com/resources     Some of the links there support my internet educational outreach. And it's appreciated. 

There are more resources for you. But for this article, it's enough for now. Subscribe to the Newsletter of Fish and Koi Diseases Diagnostic Treatments and Cure. I'll update about once a month and will never send an advertisement. 


Doc Johnson


What is the Most Important Fish Water Quality Parameter?

Some would argue that it's Ammonia. The FIRST product of the nitrogen cycle and the primary waste product of fish. 

Environmental Threats to Goldfish Health.

Youtube Video about Ammonia with Dr Erik Johnson

Goldfish health is impacted by far more than just the ‘way’ we care for the fish, or the parasites they may contract. Indeed, their very environment is often the greatest threat to their survival. This is especially true in new, unbalanced systems where the new load of livestock and the relative lack of beneficial bacteria negatively influence water quality. Perhaps the greatest effort in the care of Goldfish is in the management of the precarious balance of the water quality.

Perhaps the most important element of “water quality” which the hobbyist should master is the nitrogen cycle. The “nitrogen cycle” refers to a natural process, which is carried out by beneficial bacteria. The process reduces fish wastes and excretions into harmless compounds in the environment. The “cycle” reduces Ammonia into Nitrite. Then Nitrite is reduced into Nitrate. Plants then use the Nitrate. 

Ammonia represents the primary waste product of fish, which starts the cycle as its initial fuel. Ammonia is a nitrogen-based molecule, which may ionize and de-ionize depending upon the pH in which it exists. Ammonia is more toxic at a higher pH. At a lower pH the Ammonia molecule becomes the Ammonium ion and is less toxic.

Twenty five percent of fishes’ Ammonia excretion is in the vented wastes. Another 75% of the fishes’ Ammonia excretion is via osmosis through the gills. Ammonia is not actively excreted and leaves the fish because an osmotic gradient exists between the higher physiological [bloodstream] level and the water’s natural amount. The problem arises when the water contains high ammonia levels. When the water has a high Ammonia level, the Ammonia does not leave the fishes’ bloodstream and so they die of “auto-intoxication”.

Ammonia is removed naturally from the environment by a beneficial bacterium that lives on all underwater aquatic surfaces [term: Biofilm], and in the filter. This beneficial bacterium is called Nitrosomonas. Nitrosomonas pares off Ammonia’s Hydrogen ions and replaces them with Oxygen molecules, creating a Nitrite molecule.

The need for Oxygen in this reaction is illustrated in the following equation:

NH3 + (O2 required)—(Nitrosomonas) —à NO2 (Nitrite) + 3H+


In the above equation you will notice that Hydrogen ions are liberated in the reaction. These may accumulate and depress the pH of the system. It is an illustration of how the very biological activity of the beneficial bacteria in the system can “crash” or reduce the pH.

Ammonia is a clinical threat in aquariums that are ‘new’ or have not established a colony of beneficial bacteria yet. Ammonia accumulation is a big part of the “New Tank Syndrome” and one of the leading killers of fish. Once Nitrosomonas has proliferated to adequate levels, the Ammonia levels decline and the Nitrite levels increase.

The diagnosis of Ammonia accumulations is as simple as a water test. I favor Aquarium Pharmaceuticals’ Nessler’s reagent drop-type test kit. At this writing there is a simpler pad-test, which does not require mixing of reagents.  The easiest Ammonia measurement tool.

I prefer water changes in the control of Ammonia accumulations. There is a beneficial effect for overall water quality with each water change. Fish are beenfited more by this method, and there is no adverse effect on beneficial filter bacteria with the water changes. Always be sure to dechlorinate.

In the hobby right now, perceived as a simpler method of Ammonia control, folks are using water additives in lieu of proper water quality maintenance. When Ammonia starts to rise, they apply a water additive instead of reducing Ammonia production by reducing feeding of the fish. Instead of changing water, they add toxic aldehydes to bind the Ammonia. More recently, newer and safer Ammonia binding agents are available which use Sulfide ions to bind the Ammonia and are far less toxic to fish. I am very impressed by the performance of Kent Marine’s “Ammonia Detox” however even this test gives false positive Ammonia readings after it’s application. The amazing ability of this product is that the fish perk right up, and seem to be able to ignore the Ammonia after application of the “Detox” product. A similar Sulfide molecule is used in the SeaChem® product, “Prime”.

After the application of most Ammonia blocking agents, you should use a Salicylate technology test to get an accurate reading. The Nessler’s reagent in the traditional tests tends to cross react with the bound Ammonia and the ammonia-binding agent.

The clinical presentation of fish suffering under a high Ammonia accumulation is exactly like a fish that is suffering under any other water quality deterioration, or a parasitism. Hence the need for accurate testing of this parameter so you can separate the possible causes for this ‘illness’. Ammonia is directly caustic to fish surfaces, fins, and gills. Redness in the skin, excess mucus production, depressed appetite, clamped fins and lethargy are all seen in fish living in Ammonia-rich waters.

An excellent method is to take a sponge or mat from an established tank. Wring this out in a five gallon bucket and extract as much of the green to brown ‘filth’ from it as possible. This “sponge extract” has an abundant number of nitrifying heterotrophs in it. You’d simply pour the ‘extract’ into the tank that you need “Cycled” and, within 24-36 hours, you will see tangible reduction in the Ammonia levels of the system. This method does not obviate the need for a water change or two after the application, to further improve the water quality and clarity. It would be wise to cycle an un-inhabited system this way, because when you add a sufficient quantity of the “sponge extract” initially, and for a few hours, the water becomes foul in the recipient system. If the water does not go “murky brown” you did not add enough ‘extract’ to make a difference. Of all the things you could do, short of a water change, this “sponge extract” system is my favorite.

(Video on bioseeding by Dr Erik Johnson)

Zeolites are a clay resin related to clinoptilolite, cat litter, bentonite and the water softening resins used by Culligan®. In fact, rumor has it that except for the price (Bentonite is sold by the yard or ton and Zeolites are sold by the ounce) they are one and the same.

Zeolites are put in a mesh bag and when the water flows through, the resin binds up the ammonia. This does not occur in water that has been salted to any extent, and you should be aware that the resin is rapidly exhaustible. Zeolites may be recharged a couple of times by immersion in a stiff salt solution. Twenty minutes in 3.0% (seawater) can cause Zeolites to release up to ninety percent of its bound Ammonia.

To a lesser extent, the Zeolites will release some of their Ammonia when you are salting out a ciliated protozoan. You should be alert to this if you have any Zeolite in your filter when you’re salting.

Ammonia Remedies in review

  • Water changes
  • Aldhehyde binders
  • Sulfide binders
  • Zeolites
  • Suspend or abbreviate feedings
  • Only a few bacterial adjuvants
  • Established 'Filter Extraction" Technique (Bioseeding)

Fungal Infections In Koi and Pond Fish: White Cottony Growths

Fungal Infections

Fungal infections in Goldfish are relatively common, but they always tend to represent the same thing. First, let’s talk about the clinical appearance of a fungal infection.

FungalThe gross visualization of what appears to be a fungal infection is an unreliable means of diagnosis. Fungal infections usually appear as small to large tufts of white cottony material in the skin and fins of affected fish. The diagnostic challenge is that columnaris bacterial infections and Epistylis infections are grossly inseparable from Fungal infections grossly [to the naked eye].  You need a microscope to differentiate the conditions from each other reliably. Therefore it is not surprising to note that less than 25% [twenty five percent] of infections diagnosed as “fungal” truly are.

There are several fungal organisms, which infect Goldfish. The most common fungal pathogen of the skin is Saprolegnia. Under the microscope it has a very characteristic appearance: Saprolegnia appears similar to coarse strands of hair, by the hundreds organized in clumps.

Fungal infections are clinically relevant because they occur under two circumstances. There are serious, advancing cases wherein Goldfish which have been poorly handled, chilled, and stressed develop large areas of fungal growth, which cause depression and lethargy. This kind of fungal attack is seen only in fish that have suffered such mal-handling that their immune system is depressed or completely annihilated. The fish isolate themselves and eventually die. Fish with fungal lesions and which are lethargic or obviously ‘sick’ should be treated with Methylene Blue or potassium permanganate at half dose. Half dose would mean 2 PPM [two parts-per-million].

The second relevant clinical syndrome with fungus is the relatively harmless development of fungal lesions at the site of previous trauma. In these cases the fish is decidedly energetic, eating, and the lesions are restricted ONLY to those areas which were previously damaged. These fish may benefit from direct topical application of Methylene blue, malachite green or potassium permanganate paste. However, repeated water treatments are not needed because this second manifestation of fungal attack is self-limiting.

Fungal lesions in Goldfish should be considered worldwide. Fungal organisms are ubiquitous [everywhere] in the Goldfish’s natural environment and in every aquarium in the world, no matter how clean they may be. Fungal infections are ONLY seen in fish which are immune compromised or in tissues which have been damaged and left open to attack.

Remedies for fungal infections really depend upon how the fish present. A few members of a community may be affected with minor fungal lesions and in spite of the presence of these gross lesions, they may be eating and acting normally. These fish will benefit most by minimal handling, impeccable water quality and a higher plane of nutrition.

Fish which are depressed or ‘sick’ with fungal lesions will do well in warmer water, [780F] given enticing foodstuffs such as crushed freeze dried krill, and treated with Furazone Green, Methylene Blue or Malachite Green. See the formulary for dosages on these common medications.

Protein in Koi and Pondfish Food

What Protein is and does

KoiProtein is what your cells are made of. If it's a cell, it is made of protein. The most numerous cells that are made of, and thus supply the most protein are muscle cells. But one must also remember that red blood cells and infection fighting white cells are also made of protein. People forget that these red and white cells have a finite life span in the blood stream and must be remade. How does the fish replace these cells in winter when it's not eating? Very difficult. This is one reason why Spring is often fraught with disease.

Protein is the "stuff" of muscles and so is harvested from animals in their muscle. When we eat protein in the form of beef, well, you get the idea. Beef muscle. 'Kay.

Studies have been done which compared the digestion and assimilation of protein in fish. They tested chicken protein, fish protein, plant protein, beef protein, pork, etc. And you will NOT be surprised to know that fish proteins were the BEST digested and assimilated. Fish eat fish. This makes sense because the incidence of fish leaping onto shore and eating cows is very, very low to non-existent. Fish are adapted to the consumption of others in their food chain. So fish proteins are the best for fish. Cool.

So when you look at a bag of food and the first ingredient is "Wheat". Again, you get the picture. Wheat is not equal to fish protein. So keep looking. You should look for fish or aquacultural proteins as the first ingredient in a decent diet for your Koi and Goldfish.

Fish can DIGEST corn. But they do not ASSIMILATE it as well as fish proteins, in fact they might not assimilate it AT ALL if an amino acid is missing from the protein in the food. So companies which have stooped to talk glowingly about corn being "DIGESTABLE" while omitting fair representation of corn’s comparatively poor assimilation are being misleading.

So, Plant Proteins in Koi Food Are Bad?

Au contrare! There are three common purposes for plant material in the food. Fiber, protein, and energy (carbohydrate) are all functions of plant proteins. When a company puts corn in a diet just for protein, it's sort of sad. Sad for them (who's doing their research?) and sad for the consumer.

Proteins can be lopsided.

But often, wheat, soy or corn meals are used *IN ADDITION TO AQUACULTURAL PROTEINS* to provide SOME protein and SOME energy. When used this way, it's a 'Good Thing' because proteins in corn, soy or wheat are very different from proteins in a feed ingredient like shrimp or blood meal.

Corn protein may be VERY heavy in Leucine or Lysine. While shrimp meal may be heavy in sulfur containing amino acids and very low in Lysine. Therefore, these plant proteins can BALANCE an amino acid profile to ensure that all essential amino acids are represented and make it complete. At the same time, plant proteins can contribute needed energy in the form of carbohydrates. They may also bring fiber to the equation.

So, you might see Fishmeal as the first ingredient in a diet. Then lower on the list you might see Wheat germ, or soybean meal, or corn gluten meal. Don't be put off by these dual-purpose ingredients.

Flukes or Trematodes in Koi and Fish Ponds


FlukesMonogenetic trematodes are a separate class of parasites from ciliated protozoans. The monogenea do not have an intermediate life cycle off the fish. Those trematodes that do are called Digenetic trematodes, and use a bird or a snail as an intermediate host. These are not a considerable pathogen of Goldfish and so we are limiting our discussion to the far more common monogeneans. 
The common monogenean trematodes of Goldfish are of the genus Dactylogyrus or Gyrodactylus. Sorry about the names, I did not invent them. Their mode of reproduction [egg versus embryo] and the presence or absence of eyespots can differentiate these flukes. 
Try to remember that the gill fluke Dactylogyrus lives in the dark. It has eyespots, but still has to strain to see. 
The body fluke, Gyrodactylus, lives on the fishes’ skin and has no eyespots. What I find amusing is that the body fluke and the gill fluke hardly ever exist in homogenous populations and are distributed evenly over the body. In fact, looking back at almost a decade of light contrast microscopy and surface biopsies, I don’t recall a time when I noticed gill flukes exclusively on the gills or skin flukes restricted to the body. 
The fluke derives its nutrition from the slime coat of the fish. It does not suck blood or bite chunks of tissue from the fish, but will ingest nutritive mucus via its anterior end.  
Fish that are under attack by flukes will develop an excessive slime, isolate themselves, and clamp their fins. They may also show excessive scratching and flashing behavior. Eventually, the fish may develop sores or ulcers on their bodies as a result of the scratching behavior. Flukes are also known to carry hazardous bacterial fish pathogens on their haptens. These bacteria are deeply inoculated into the skin by the haptens. I maintain that “ulcer disease” is more commonly transmitted by flukes than by any other vector. In fact, the clinician would not be committing malpractice to assume that any fish which feature bacterial ulcerations in the body are, (or have been), parasitized by Flukes. 
Flukes can also do considerable damage to the gills of fish. With their hold-fast haptens deeply embedded in the gills of the fish, they can trigger Bacterial Gill Disease through three mechanisms. 
1) Direct trauma, chronically bleeding the fish out.
2) Indirectly causing stress, which potentiates the Bacterial Gill Disease outbreak.
3) Direct inoculation of the bacterial pathogen into the gill tissue. 
The microscopic appearance of trematodes [flukes] is extremely characteristic and it would be almost inconceivable that one would mistake a fluke for any other pathogen. They are the largest pathogen for which you would employ a microscope. They are easily witnessed at a combined power as low as 40X [forty times]. The fluke is an elongate [tubular] parasite with suction cups on one end and a gripping end which features a ring of small hooks which fan out around a pair of vicious looking hooks; the haptens. Inside the body of the fluke one will observe either a nondescript egg which is typically oval, or the observer might see a complete miniature of the mother. Indeed, in the early research done on trematodes of this nature, scientists were amazed to dissect as many as four generations of embryos from within one adult fluke. 
I maintain that flukes are the most compelling argument for owning a microscope. Let me explain. If you did not want to buy a microscope, you could use salt as a blanket treatment or panacea and you’d be “covered” in the instance of at least seven common pathogens. If you coupled that with Dimilin© or Lufenuron, there is only one parasite that would be left behind by this regimen. That sole survivor would be the Fluke. Since the flukes only have a mode of treatment which is either expensive [Praziquantel] or risky [Formalin, KmnO4] – then I would recommend the microscope to prove or disprove the necessity of these flukicide treatments. 
There are several ways in which the trematode life cycle impacts how we treat them. In the first place, the mother fluke often contains several future generations of young. Depending upon her species, she may carry a durable egg. The impact of this is that one might kill the mother with some waterborne treatment, and her body may remain on the aquarium bottom until such time as the egg or young will emerge from the remains of the mother and seek out a new host. This is the reason I recommend a repeat Fluke treatment approximately four days after the first one. 
In the second instance, we also know that this young trematode swarmer must find a viable host within a short time or it will die. This is how one can bypass the filtration system during treatments that would otherwise disable the nitrifying bacteria. Let’s work an example. 
During your first potassium treatment, it’s recommended that you would bypass your filter. Common sense might leave you wondering if there are parasites hiding in the filter, safe from the treatment. Indeed there may be. When you resume the filter, these parasites move out into the aquarium and resume the infection process. If they did not exit the filter, they would die of starvation. During your second treatment, there will be no parasites in the filter when flow is suspended. If there were, these would only be senescent adults. No larvae will have had time to re-emerge and be in your filter. Still, a third treatment (irregardless of whether you are using Formalin or Potassium permanganate) is recommended “just in case”. Understanding the life cycle of the Fluke is important in the determination of your treatment regimen. The recommendations I give you are not empirically derived. 
Additional scientific research has revealed an interesting result. It was found that a closed population of fish could not support Flukes indefinitely.  Indeed the fish seemed to develop specific surface immunity, which eliminated the flukes gradually. Only by introducing immunologically naive fish to the group did they maintain a viable, expanding population of flukes. The significance of this study is that if you “close” your Goldfish collection and resist the urge to bring in un-checked or un-quarantined fish, you might be able to avoid sustaining or introducing future fluke infestations. 
See:  Scott, M.E. & R.M. Anderson, Parasitology, 89 (Pt 1):159-94 1984 Aug.

Tadpoles and the Pond


TadpolesControlling amphibians is not easy – but hatcheries try to control them, especially tadpoles, because the tadpoles take up space and use valuable resources in terms of oxygen, food, while contributing to waste production, for no net financial gain for the farmer. 

Control: The growers try their hardest to catch the tadpoles while in the "egg mass" – these appear as gelatinous masses floating in the water with small black spheres in there. They slurp or net them up – because they know that if they don't intercept the eggs; the tadpoles themselves are REALLY tough to get out of the ponds. I saw a Border Collie dog once, that was trained to bark at the egg masses, and then they had a guy on a four-wheeler who'd come by and get the eggs in a net.

Tadpoles already hatched?  Here's what some of the big growers do – they buy or catch Blue Gill or Crappie pan fish, which can also be caught in traps with corn. You want these carnivorous fish to be about the *same size* as your Goldfish, as they WILL antagonize your Goldfish, if they are small enough. Bass are worse to beat on (or even eat) goldfish and small Koi, but they work. 

I've been told that (Channel) catfish work well for tadpole reductions. I don't doubt this, however I believe that the pan fish work better in several ways, or else the breeders and growers would use more catfish, and I don't know of any hatcheries using catfish for tadpole control. 

If you go to the ornamental wholesale or hatchery you'll see one, or MAYBE two, three-inch Blue Gill or Crappie per one hundred Goldfish. So you don't need any kind of "school". Some people would warn you to keep only one fish per species so that you never risk them breeding – because they get violent MOSTLY if not only when they're ready to breed and protect their territory, eggs and fry. Other people have recommended some baby small-or-large mouth Bass. BE CAREFUL! Bass definitely eat more tadpoles than the pan fish do, but they also grow very fast – they will grow very fast on a diet of tadpoles and get big enough to eat or henpeck your desired fish. 

So, that's what I'd suggest. ONE or two Bluegills. Or a baby small mouth bass. Remember, you *can* introduce disease on any new fish, including your tadpole regulators, so they should be quarantined just like any other fish. 

PS: It's a common question whether salt hurts frogs and tadpoles. The answer is: Not at the usual 0.3% or 0.6% salinity. 

Use of Salt Against Parasites

This may be the most important article / video folks will see this Spring because for a LOT of people with sick fish, SALT at 0.3% may be the fastest and easiest way to limit fish losses AFTER testing the water to make sure it's not as simple as a low pH (ha ha ha)

If it's NOT water quality, maybe it is a parasite and MAYBE you can nail it down with Salt. 

Here's how. (Using Salt to Control Parasites and More)


Posted on

You Should Know The Cycle

If you are not already familiar with the CYCLE, this is the process by which fish wastes and other debris are broken down by bacteria in an aquatic system. Let’s trace it here.


The Cycle is a short series of bacterial reactions that purify water.

Ammonia is produced by the fish, from gills (75%) and vent (25%).

*Nitrosomonas* bacteria in the gravel break the Ammonia down, *before* it has a chance to accumulate and harm the fish.

This results in the production of Nitrites.

*Nitrobacter*, a second cousin bacteria, breaks down Nitrites into harmless NitrAtes before the Nitrites can accumulate and harm the fish.

The Nitrates are simply plant and algae food. In the presence of phosphates, plants use Nitrates to grow, but without the plants, Nitrates could accumulate and cause sickness (Bloody fins and weakness) in the fish.

So you can see that since Ammonia, Nitrite and eventually Nitrate have hazardous effects on Koi, it is necessary for you to use normal testing procedures to detect these intermediates whenever fish are sick.

The Cycle takes 4-6 weeks to complete under normal circumstances but t’s possible to cut it down to about three days with BioSeeding. That is a technique, not a product. It’s described in this website.

Be sure to see the video on BioSeeding (video) and consider it when rushing the cycle.

Posted on

Fish Medicine, Disease, Symptoms and Cure

Don't forget about the Youtube Channel that supports Koivet.com in the mission to educate (especially in time for Spring) when pond fish diseases get out of hand. 

Youtube for Fish Medicines, Diseases Symptoms and Cure

Also, don't forget about the book, Dr Erik Johnson's Koi Health and Disease 2 

Finally, if you have not seen the section in Koivet about "twenty steps to pond fish health" it's a section of Koivet that takes you "step by step" through an orderly process to lead you to a clear picture of why your fish or pond is "sick" and it starts with water quality. (Video version)

I've uploaded a video that's a favorite of mine, lately. It's about Adding Beneficial Bacteria to Aquariums to speed the cycle. It's an established nitrification system with no break in, over night. 

Posted on

Check Out The Youtube Channel

In case you missed it, I've got a growing Youtube channel with all my fish health videos and it's growing all the time. Doc Johnson's Youtube Channel for Koivet.com 

Also, Koivet.com is being overhauled to a WordPress theme to be the best fish health, fish medicines symptoms and cure web site out there. Videos and pages melding into a comprehensive "course" to bring you up to speed with "what you should know" videos and pages. 

Finally, I have my book on amazon.com which means if you have prime you can get Koi Health & Disease 2 overnighted in the event of an emergency. 



Posted on