John Satisfaction Syndrome, Aeromonas Bacterial Pitting

Posted in Health and Disease

By DocBottom

Deceased Oscar showing severe John Satisfaction Syndrome

'John Satisfaction Syndrome' is current parlance for the collection of symptoms associated with an infection of Aeromonas bacteria in the oscar. This is not an official term and your veterinarian or fish store worker is unlikely to recognize it.

Aeromonas bacteria are gram-negative, facultative anaerobic motile rods. Gram-negative just means you cannot stain it with crystal violet dye. Faculative anaerobic means that it can survive in conditions without oxygen but does not require an oxygen-free environment. Motile indicates that it can swim around. It is rod shaped. Essentially, it looks like a hot-dog with a string tail. A number of species have been described.

Aeromonas is ubiquitous in water and soil and is not normally considered a disease-causing organism. However, it is able to infect wounds and could cause a systemic infection in immuno-comprimised individuals, but healthy animals are unlikely to be made ill by Aeromonas, in spite of it being present more or less everywhere.

One species, Aeromonas salmonicida is of economic importance because of its tendency to attack salmonids, creating Furunculosis, characterized by blisters or boils on the skin of the fish. This illness is seldom seen in the wild, but is a common and potentially disastrous problem in salmon and trout farms, where the crowded fish are less able to maintain healthy immune systems.

In the ornamental and pet fish trade, Aeromonas is not well-known, but some veterinarians who specialize in treating fish believe that Aeromonas is responsible for a large percentage of cases of bacterial dropsy. (Dropsy cannot be considered a disease in itself, it's what kidney and liver-failure often look like in small fish.)

When my oscar, John Satisfaction, started to develop holes in his gill-cover at only a few months of age, I believed it was HITH, but could not understand why a disease caused by poor water-quality would effect a fish living in excellent water conditions. I treated him with Metronidazole, supposing there might be some truth to the theory that Heximata causes HITH (This isn't likely, HITH is caused by poor water quality and diet, but the flagellate protozoan Heximata may cause a secondary infection in HITH wounds.) Metronidazole was not effective, and I began to suspect a bacterial infection. I then treated John Satisfaction with an antibiotic, Doxycycline. This also failed. Feeling that time might be short, I took a culture-swab from my fish's wounds and sent it into the Idexx veterinary diagnostics lab for a culture and susceptibility test. This means that the guys in the white coats took the swab from John's wounds and grew whatever they could get off it in a dish, and then sat around dribbling tiny amounts of different antibiotics on it so they could tell me what killed it at the lowest concentration.

The bacteria infecting John Satisfaction was Aeromonas veronii biovar sobria (which is not the same as Aeromonas sobria) and the drug that destroys it best is Enrofloxacin (sold by the Bayer corporation under the trade-name Baytril.) I treated my fish with injectable Baytril and after a lengthy and difficult time, was able to effect a cure. He is now fully healed. During the entire illness I used as a diary of my fish's condition, which is why “John Satisfaction Syndrome” is its popular name here. Afterwards, I enlisted the help of users in collecting data about how this illness may appear in Oscars, and how to effectively treat it.

Aeromonas veronii biovar sobria is a normal constituent of the gut-flora of leeches. It helps them to digest blood and they could not live without it. I believe that John Satisfaction first got the disease from being bitten by leeches and that I was not able to see the old and only mildly infected bite-sites until he was bigger, by which time it had managed to spread to his gills, and thus effect the gill-covers. However, it’s possible that other cases of John Satisfaction Syndrome have been caused by different Aeromonas species. They are similar enough that for our purposes, it doesn’t really matter.

So, does my fish have JSS?


Skin ulcers

These appear as deformed discoloured scales. Typically they are ashy grey in colour. In the case of John Satisfaction, it looked as if someone had put a cigar out on my fish's side, giving it a hard twist. If one looked very closely, with a magnifying glass, one could see that the middle of each ulcer was covered with a great many tiny pinprick holes.

Another user reported a lesion on an area where the scales are smaller. It was grayish white and had a pebbled/cottage cheese appearance.

In advanced cases, these skin ulcers go through to the flesh and may be red, resembling “Fish TB.”

John Satisfaction's 'cigarburn' skin ulcer

HITH-like holes

This is a critical diagnoses factor. HITH normally effects the area around the nostrils and above the eyes first. In the case of John Satisfaction, the holes appeared on the gill covers. Holes appearing on the gill cover “first” suggest bacterial pitting, not HITH. This makes sense, because Aeromonas finds the gills to be the easiest part of a fish to colonize, followed by the skin, then the cells lining the guts. I believe that in John Satisfaction's case, Aeromonas traveled from the infected skin around old leech-bites and colonized the gills, then moved to colonize the sensory pits on the gill-covers. At its worst, holes began to develop around John's nostrils, but it never reached the rest of his head.

The holes may heal over with a thin layer of skin, and then reopen.

They may appear to fill in with a super-thin layer of orange-yellow tissue. This looks like healing, but is not. Aeromonas is actually a pale orange colour, if the colony is large enough it looks like the fish has begun to heal and that the new tissue is the orange-red colour typical of red areas on the common oscar colour-varieties.

John Satisfaction's gill-cover holes

Weird Jelly-Like Blobs

These get on the fins, and seem to be how the skin lesions appear when the fin tissue is first infected. It looks remarkably like a grey-brown leech, semi-transparent but speckled with opaque spots. Later it will disappear, leaving a hole in the fin where it was.

Lethargy and loss of appetite

These are symptoms of almost any major illness.

Bubbles coming out of the gills

The digestive action of Aeromonas (and many other bacteria) produces carbon dioxide. When John Satisfaction was at his worst, tiny bubbles appeared from his gills and the holes on his gill-covers, constantly. This isn't common to all, or even most, cases of what we believe to be JSS, but it's a good indicator that a hole is not HITH, unless you have a bubbler in the tank and the fish is getting bubbles caught in his holes by sticking his face in the stream of bubbles.


That's when the fish becomes bloated. The scales may stand out like those of a pine cone. It's a symptom of kidney failure. If this happens, probably the disease has destroyed your fish's internal organs and he is near death. Even if the infection is cured at this point, the fish will not recover.


Aeromonas is resistant to penicillin-family antibiotics and to erythromycin. It is partially resistant to tetracycline-family antibiotics. This means that the fish medicines commonly available in pet stores in the United States will not work, unless you get a tetracycline-family one and use a higher dose for a longer period than the manufacturer recommends, a course of action that might be dangerous to your fish.

Aeromonas is susceptible to aminoglyoside-family antibiotics. This family includes neomycin. There are three commercially available fish medications containing neomycin:

Gel-Tek Neomycin

This is a medicated gel-based food. Normally, feeding an antibiotic to a fish is a better way to deliver it than a tank treatment, but unlike other antibiotics, neomycin is not absorbed well through the digestive tract. This medication might clear the fish's guts of Aeromonas infection, but infection on the skin and gills may remain. If the fish is still eating, this formula may be worth using, but only in conjunction with another treatment.

Hikari Bio-Bandage

This is an ointment. You have to take the fish out of the water, partially dry off its skin-lesions, and put the Bio-Bandage liquid on. This is a pain, and it cannot be used on the gill tissue. Since any fish infected with Aeromonas on the skin is likely to have it on the gills, Hikari Bio-Bandage is unlikely to completely cure the condition. It may be worth using in conjunction with another treatment.

Seachem Neoplex

This is a neomycin-based tank treatment. Because the medicine will be free-floating in the water, it should come into contact with the entire fish, skin, gills, guts and all. Seachem Neoplex is the treatment of choice for people who are not willing or able to enlist the services of a veterinarian. Most fish stores do not stock it, but it is available from Big Al's Online. Several users have cured their fish of JSS using Seachem Neoplex.

Addendum: And now it appears that a larger number have found that 'Neoplex' didn't do anything. I suspect it depends on whether or not the disease has moved on to infect internal tissues, where Neoplex can't reach it.


Aeromonas is extremely susceptible to fluroquinolone-family antibiotics. Enrofloxacin (Baytril) is one of these. These drugs are not available in the US without a prescription. You will have to go to the veterinarian. It may help to print out this article and show it to your vet, you may be able to get a prescription without bringing the fish in.

Baytril is an injectable, and you will either have to bring the fish in for the vets to inject, or inject it yourself. This is not as difficult as it sounds, but isn't exactly jolly fun either. Inject into a muscle mass. Try to get between the scales. Keep in mind that it may be very difficult to pierce the scales, but the muscle underneath is quite soft. This can be startling, because you will be pushing hard and suddenly the resistance will be gone.

The dosage is by weight, so you will have to remove the fish from the water and weigh it first. Use 5 milligrams of Baytril per kilogram of fish. It will be a tiny injection, because Baytril injectable is typically 22.7 mg per mL, and Oscars do not normally reach a full kilo in weight. I injected my fish daily, but another user injected every other day, on the advice of his veterinarian. I believe this veterinarian is more up-to-date than the resources I used, so I advise the every other day regimen. Baytril's side effects include a loss of appetite, and John Satisfaction suffered severely from that, while the fish receiving the every-other-day treatment did not.

Baytril is available in a tablet form designed to be palatable to dogs, but I am not sure of the dosage for oral administration of this drug to a fish. Your veterinarian may know, and it would be possible to grind up the tablets and mix them into fish food.

It may be desirable to treat with Neoplex during the last week of a run of Baytril injections, and during the week following. The two antibiotics potentiate each other, and because it is a tank-treatment, Neoplex can destroy Aeromonas that are free-swimming in the water, lessening the risk of reinfection.


Another possibility, as yet untested, (at least so far as knows) is to use the aminoglycoside antibiotic Gentamycin as a tank treatment. It is available through your veterinarian and may be added to the tank water at a rate of 4-5 milligrams per litre of water.

Length of Treatment

Normally, a veterinarian will recommend that one treat with an antibiotic 'past the cure,' meaning that the patient appears fully healthy before you stop giving the drug. This prevents relapses and prevents the development of strains of antibiotic-resistant bacteria. Unfortunately, several people, including myself, have found that wounds caused by Aeromonas are extremely slow to heal. I treated John Satisfaction with injections daily for twenty-four days and saw no result except that the wounds stopped getting bigger. John Satisfaction was suffering from anorexia and had not eaten for over a month, and I believe this prevented his healing. A week after I stopped giving the Baytril injections he began to eat again, and visible healing started. It proceeded very slowly. I treated with Seachem Neoplex at this time and continued to use it for four weeks (one week longer than the manufactuer recommends) and the wounds were still not fully healed when I stopped treating with Neoplex. I believed that they would prove permanent scars, but over the months following they have healed up nicely. When the question of when to stop treating arises, you'll just have to make the call, based on your fish's progress, or ask your vet. Antibiotics can damage your fish's liver and kidneys, but this is hardly worse than death from bacterial infection, and stopping antibiotics too early might create a new strain of bacteria that are resistant to the antibiotic. It's a tough choice.

Zoonotic Potential

It is not very likely, but you could be infected with Aeromonas yourself. I advise you to wear gloves when handling any fish suspected of having this infection, and to wash your hands afterwards regardless of gloves, and treat any small wounds on your hands with a neomycin-based antibiotic ointment (Neosporin or any triple-antibiotic ointment, commonly available from the grocery store.) If you are immuno-compromised, get somebody else to take care of the fish and the tank; avoid all contact with the tank water.

I would like to thank Dr. Amber Clark and Dr. Kristen Woestehoff for their assistance in treating John Satisfaction, and Dr. Sam Stiver of Idexx labs. I would also like to thank the many users who have offered helpful advice in caring for my fish, researching his illness, and collecting data and photographs concerning this disease.

Help improve this article! If you have any additional images or data about Aeromonas in oscars, please contact me. (Doc Bottom)

Kmuda's Note

Since the inception of Doc's Article, we have had experienced a couple of instances of early stage “JSS like” symptoms being cured by Kmuda's Bacterial Pitting Treatment. If caught early enough (when gill pitting is first noticed), JSS may be cured by this treatment. So the recommendation is to give it a try and if it does not work, seek a vet's assistance.