Treating Skin Ulcers on Fish - Page 2: Severe Ulcers

Treating Skin Ulcers on Fish - Page 2: Severe Ulcers

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Treating Skin Ulcers on Fish
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The third case is one of our Uaru amphiacanthoides. This was a case of a severe, life threatening ulceration. Here is what happened:

We keep a pair of Uarus in a 250 lit tank, with a small colony of Leporacanthicus joselimaianus.  We would describe the tank as an established one in excellent condition; 80% of the water is changed religiously every week and there have been no new additions to it whatsoever (plants, fish, decoration etc) for over two years. The Uarus enjoy swimming in the open quite often though if people are around they prefer hiding under an arched piece of wood or between the two internal filters of the tank and watching from there the happenings.  As a result we are not particularly worried if we do not see them out often. The food is dispersed by an automatic feeder so all in all the fish live an undisturbed life without much interference from us.

Over the summer we have been away and the standard of the tank maintenance was significantly lowered. In real terms there were no water changes for four consecutive weeks. We returned to find all the fish looking fine. About a month later we noticed one of the Uaru's staying a bit too much in the open, near the front glass. We quickly checked to see if the fish was ok (this behaviour was very untypical of him) and saw what appeared to be a small scrape on upper part of one of his sides, near the dorsal fin. We thought he could probably have been involved in a tiff with one of his tankmates or scratched himself on the wood in the tank and paid no further attention to it; the fish was bound to heal by himself. 

A week later we saw the fish again, this time hiding between the pumps. We can only say he was in a state. He was particularly pale (a very pale and dull shade of green),  most of his fins were almost missing and his tail was also eroded.  We immediately performed a massive water change in the tank, cleaned the filters and added antibacterial medication (Esha2000) combined with Esha Exit to prevent secondary infections such as ich etc. A week later, when the treatment ended, we found the Uaru on the substrate, totally white, with snails all over its body.... 

Yes, we thought he was dead. As we tried to remove the body however, he moved!!! The fish was alive but clearly on his way out. We quickly discussed the issue - the humane option appeared to be euthanasia.  The fish was really in a bad way: he had no colour, no fins, no tail and there was a massive ulcer along his dorsal and ventral fins on both sides.  More over he could not swim anymore - he could only lie flat on the substrate. The other tankmates, including the second Uaru, were fine. Interestingly enough, while the two Uarus were always inseparable, in this instance the healthy one would not come near the affected fish. Instead he placed himself firmly at the other side of the tank and kept well out of the action. Though normally you would expect the tankmates to isolate a poorly fish, we note this incident as interesting because, in our experience, in true pairs healthy partners always look after their ill partners and stay by their side to fend the other fish off. Not on this occasion, though.

We decided to give the little fellow a chance and try to reverse the situation. We put some tank water in a big bucket, took him out of the tank and put him in the bucket.  We carefully removed the snails from his body to ensure no further damage was done on his slime coat. We then proceeded with a massive water change and, once again, cleaned the filters and as much of the substrate as we could. We added 2ppt of salt in the tank water and treated the fish by spraying first TAP Aqua Swab on the wounds, then Aqua Gel. This was tricky because the wounds were all around the body of the fish, so we had to make sure we pumped the gel through the net, then carefully spread it out with our fingers. While the gel was drying we quickly rearranged the tank to ensure there was an arched piece of wood at the front, near the glass. The "cave" had no access from the back as we placed some rocks and wood there. The ill fish was then put back in the tank, inside the cave, to enable us to see him and stop his tankmates from disturbing him.

We treated him with Aqua Swab and Aqua Gel daily for three days while we continued adding salt to the water (pot daily) until the total concentration reached pot. On the fifth day, to our delight, we found him swimming over the wood on our return from work. His balance was still not good and on occasions he dipped head down or on his side, particularly when he was trying to avoid us netting him for his treatment. Yet things looked promising. The other UAR still kept away from him.


We continued with our water changes and kept the salt concentration to the same level the following week.  At the end of the second week of treatment we started treating only with Aqua Swab once every 3 days. Aqua Swab is quicker to apply and we wanted to stress the fish as little as possible. 


At the end of the third week of treatment the two Uarus were swimming together while our patient was becoming quite successful in his efforts to avoid being netted. We ended up moving most of the wood and caves out of the tank to make sure we could catch him without him hurting himself by trying to squeeze through narrow openings or us stressing him - and the other fish - too much.


It took four weeks for the fish to show clear signs of recovery and stop swimming erratically. The improvement was visible though slow. The ulcers on the body healed first whilst the skin on the rays took longer to grow back. We knew that the fish was on the way to recovery as the rays were clean, without indication of deterioration or fungus.


On the 4th of November most of the ulcers had healed or showed clear signs of improvement and the membrane started reappearing on the fins and - partly - the tail. The two fish were constantly together again - which was the most encouraging sign in the circumstances. We stopped the local applications with Aqua Swab but continued with the salt treatment. We lowered the salt concentration to 5ppt just before Christmas and we gradually started reducing it by 1ppt weekly at the end of January. In February 2010, 4 months after the ulcers were first identified, the fish is healthy and looks fine though some scarring is still visible. It appears this will take some time to be fully healed. (7)


As expected the more he was recovering the more difficult it became for us to approach him, net him or take photos of him. To date the fish is still swimming for cover every time we approach the tank. This is not an issue, however, as we are confident he will, in time, trust us again.

Again, the treatment of this fish varied slightly from the one applied / recommended in the previous two cases indicated. For a start, the salt concentration in the water was considerably higher. This was justified by the extremely poor condition of the fish when we started applying the treatment. This is one of the few cases we can say with absolute confidence that if it was not for the salt the fish would have had an osmoregulatory shock and would have died.  (8) For this reason we kept the salt concentration in the water quite high for a long period of time (about two months) after the fish had recovered. It was imperative, we felt, to keep the fish as stress free as possible for a sufficient amount of time to help him convalesce fully, prior to withdrawing the support (salt).

Due to the severity of the ulcers on the Uaru, in addition to the fact that we did not know exactly what caused the ulceration, we sprayed the wounds with Aqua Swab prior to applying Aqua Gel. Aqua Swab cleans the infected area and prepares it for the subsequent application of Aqua Gel. We continued the treatment with Aqua Swab following the applications of Aqua Gel just to keep the affected areas clean while they were healing.

As the Uaru had extensive ulcerated areas on both sides of its body we made sure we sprayed both sides with Aqua Swab but we only treated one side at a time. This was to ensure that the medication would stick well to the ulcers, rather than risking to try to apply medication on both sides of the fish and ending up with incomplete applications all over.

When doing our weekly water changes and tank maintenance we kept the fish out of the tank, in a bucket with tank water. We returned him to the tank once the water change was over and the pumps cleaned. This was to ensure that the new water would not dissolve the medication but also that the fish would not have to try to cope with low water levels in the tank (trying to hide under the wood may have caused more scratches, damage etc.) Water changes were not done with continuous flow, as usually. We lowered the water as much as possible (leaving just enough to cover the body of the other Uaru) and refilled the tank with water at the right temperature and the correct salt concentration.

Finally, as with the other cases, we stopped the application of Aqua Gel when the redness (infection) disappeared. Important as the application of medication is, the fish do get stressed when netted and taken out of the water. It is important to balance the two to ensure that the fish is not stressed any more than what is absolutely necessary.  Medication is applied to address the infection. Once the infection subsides an otherwise healthy fish in good condition will heal itself without further support.

The final case is the case of one of our Datniodes pulcher. Again we keep two fish (hopefully a pair) in an established 1000 tank, to which there have been no additions for over 4 years. The fish are growing beautifully and are in excellent condition; they interact with us very well. 

These fish get fed by hand every other day; they eat frozen food only (small fish, prawn, mussels and chopped calamari).  They both have a good appetite so we were a bit surprised when the smaller of the two (TL about 30cm) did not come for her evening meal on one occasion. We did not think much of it but got a bit worried next day when we noticed she was not at the front of the tank watching us. The day after we managed to "persuade" her to come to the front and we noticed that she was quite pale and had a pretty bad ulcer on one of her sides, covered by an off-white substance which did not appear to be fungus - it was more like mucus. 


You know the rest. We checked the tank quickly and got reassured that this was an isolated incident. The other fish looked fine. We could only suspect this started by the fish getting a cut or graze coupled with the fact that the ulcer appeared a week after our Christmas break, during which the tank there were no water changes for three weeks as we were away. We immediately started a big water change (80% of the water). Once the tank was filling back up we got her out and patted the affected area with a clean piece of kitchen roll. Interestingly enough we noticed quite a lot of tiny particles of some black matter that stayed on the paper. We cleaned the area again thoroughly with some more clean paper and aquarium water, making sure the water moved the particles away from the body of the fish. We patted the area dry, applied Aqua Swab and Aqua Gel and released the fish in the tank.


We repeated the same procedure during next application and noticed there were considerably less of the tiny black particles on the wound. Prior to the third application the paper towel was totally clean; no black particles were on the wound. Following this we monitored the fish for a couple of days and it showed clear signs of recovery. Its colour was gradually returning to normal while the infection had gone. It was just a matter of waiting for the scar to disappear, which does not require further application of medication.

Unfortunately we do not know what the black particles on the ulcer were. Maybe knowing what they were could shed some light on the cause of the ulcer.


In all the cases above we were lucky in that the ulcers were localised instances on individual fish in different tanks. They were infected wounds rather than the outcome of a systemic infection so we did not need to treat the fish with antibiotics. When dealing with ulcers it is important to check the progress of the affected fish and its tankmates daily; if it appears that the fish does not respond to the treatment applied it is advisable to isolate it and consult a vet. If other fish get affected too you will need to consider treating the tank water in addition to the affected fish. It may be that your fish need treatment with antibiotics to address the systemic infection causing the ulceration. The same applies for recurrent ulcers or ulcers accompanied by other symptoms of bacterial infection such as pop-eye or dropsy.

In some cases it may be advisable to clean the ulcer using a specialised procedure. This could involve removing loose scales or part of the dead or infected tissue around the wound to promote healing. Some LFSs in the UK, particularly Koi specialists, offer this service. In all other cases a visit to the vet is required. 

Whether the ulcer is caused by a bacterial or a viral infection a good water change should always be the first step in treatment; continue with your water changes religiously for the duration of the treatment. Remember that the water may look clean to you but bacteria and viruses are not visible; there is one thing that is certain and that is that your fish got an infection, which means the water conditions are not pristine. Viral infections are not treatable; it is generally thought that the best way to 'treat' a viral infection is to improve aquarium hygiene and the diet of the fish. (9) Under favourable conditions the immune system of the fish has a fighting chance against the infection.  Antibiotics for bacterial infections are available but it is worth remembering that very few vets are fish specialists and there may not be one in your area. So read up before you visit and be prepared to discuss the situation with your vet.  Specialist or not, your local vet can help in that s/he can carry out procedures you cannot (such as small operations) and s/he can prescribe medication which you cannot otherwise lay your hands on.

More importantly, as a final step, reconsider the conditions of your aquarium and, if appropriate, address any problems (overcrowding, poor hygiene, poor diet,  inappropriate water chemistry, stress due to inappropriate environment or bullying among tankmates etc) to avoid reoccurrence of the ulcer. If it was simply a case of opportunistic bacteria attacking the fish through a cut that happened by chance in the tank there is not a lot you can do to prevent reocurrence; but before you can put your mind at rest make sure this was the case indeed.

Photos by the authors except where otherwise indicated in the captions. 

References - Notes

1. We refer here to parasites such as argulus (fish lice) etc.

2. See the relevant discussion in When the Going Gets Tough ...

3. Dr Peter Burgess, "Ulcers - The FAQs", Federation of British Aquatic Societies

4. Examples of bacteria that cause ulcers:

  • Aeromonas, Pseudomonas and Vibrio. These are common causes of ulcers in aquarium and pond fish. Several species and strains of these bacteria have been implicated. For example, an ulcerative disease of Goldfish and Koi ('Summer Ulcer Disease') is caused by Aeromonas salmonicida subspecies achromogenes.
  • Flavobacterium (formerly known as Flexibacter). This ulcer-causing bacterium is also responsible for the condition known as 'mouth fungus' (Columnaris Disease).
  • Mycobacterium species. These bacteria are responsible for a chronic wasting disease in fish known as 'fish tuberculosis' (fish TB). In addition to skin ulcers, symptoms of mycobacteriosis may include: pop-eye, body wasting, stringy faeces, colour fading and, in some cases, bent spines. Mycobacteria invade the fish's internal organs, making the disease difficult to treat using commercial antibacterial remedies from the aquarium store. By the time outward symptoms are noticed the internal organs may already be badly diseased, and the fish's chances of survival are slim. Antibiotics generally offer the best chance of a cure -but only a minority of cases successfully respond to treatment.
  • Some viruses can also cause ulcers. Unfortunately, viral infections of fish are often hard to diagnose and cannot be treated using aquarium disease remedies or antibiotics.
    If a virus is suspected then isolate the affected fish and provide them with optimum water conditions and good food: this may help the fish's immune system to fight off the virus.
Quoted from Dr Peter Burgess, Ulcers - The FAQs, ibid.

5. Bacterial Ulcers - A Threat to Fish Health, Fishdoc

6. TAP Aqua Gel (Heals Ulcers) and Aqua Swab (Cleans Ulcers) are products of Technical Aquatic Products Ltd, a company registered in Bristol, England.  They are UV safe. We understand that currently the products are getting repackaged to conform with the latest EU regulations. They are available OTC from local Aquatic stores. The bottles have a photo of a Koi but do not let that deter you from using them on tropical fish, they are superbly efficient (as is usually the case with the well researched Koi medication).  This is the only OTC medication we have found to date to be effective on ulcers. Other medication listed to treat ulcers includes Kanamycin, antibiotic and anti-fungal baths containing phenoxyethanol, solutions containing malachite green sealed with a gel or starch based paste to protect the wound from the water etc. We found most antibacterial solutions which are available OTC to be totally and utterly ineffective. It is possible that the bacteria we are dealing today with are resistant strains. However, we are suspecting that this is not quite the case; the problem is contemporary legislation. Essentially when it comes to medication almost nothing which is strong enough to be effective  is now available OTC. This is a pity; hobbyists find themselves in a situation where they know that whatever they can buy from their LFS will be too weak to address a specific issue successfully while on the other hand there are not enough specialized vets willing to prescribe appropriate effective medication for home use. Add to this the fact that in most cases it is almost impossible to carry a diseased fish to the vet, at least the same way one carries a sick cat or dog. One wonders when governments pass animal welfare and animal rights acts whether they have thought of the fish that are condemned to death because their carers cannot access appropriate treatment. Surely there is a way around this - even if that involves an aquarist providing proof of identity and signing for specific doses of appropriate medication at specified aquatic stores or at the chemist's.

7. Healing time depends on the fish, the type of ulcer, the general conditions of the tank etc. It is generally thought that ulcers, provided the infection has been treated properly, will heal anytime up to 8 weeks. Higher temperatures promote the healing process as these speed up the metabolism of fish. We noticed that the ulcers on the body of our Uaru healed first, followed by the tail and the dorsal fin. It took longer for the ventral fin to be regenerated though this may have been just due to the fact that it was more severely damaged in the first place.

8. Ulcers are open wounds. The exposed tissue is not protected by the skin which regulates the amount of water filtering through to it. When the tissue comes in direct contact with water it allows it to penetrate it, moving from an area of high water concentration (tank or pond) to an area of low water concentration (the body of the fish). To keep the physiology of the fish stable, its kidneys then start working intensively to excrete the excess water. The addition of salt to the tank or pond water reduces the difference of the water concentrations between the tank and the fish, which in turn reduces the rate at which water enters the fish through the ulcer. This maintains the kidney activity within an acceptable range thus reducing the overall stress of the fish.  

9. Soak the food of the fish in a couple of drops of liquid Vitamin B-6 during treatment and for a month afterwards in severe cases. Check the ingredients of the food on the packet as you may need to vary the diet of the fish or change to a different brand.

10. Ulcers occur on fish in nature, too:
Noga, E. J., Review Article: Skin Ulcers in Fish: Pfiesteria and Other Etiologies, published by Sage on behalf of the Society of Toxicologic Pathology
Law, M., Differential Diagnosis of Ulcerative Lesions in Fish, Department of Microbiology, Pathology, and Parasitology, College of Veterinary Medicine, North Carolina State University, Raleigh, North Carolina, USA