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Dr. B.
Dr. B., Board Certified Veterinarian
Category: Veterinary
Satisfied Customers: 20611
Experience:  General practice veterinary surgeon with extensive experience in a wide range of species.
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We were away for six weeks and came back to find the housesitter

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We were away for six weeks and came back to find the housesitter had not cleaned the pond filter or bottom of pond and the waterfall was stopped for weeks (a small two-koi pond). One koi was gone. The other large koi (about 14") has been at the bottom of the pond with noticeable swelling near the tail, which looks fairly symmetrical, but perhaps slightly more on one side. After putting the pond and water parameters back in good order, he moves more. He does eat and perhaps did while away and housesitter threw food in without seeing fish. We bought another koi for companionship to get him moving, knowing perhaps he could contaminate the other if that kind of problem. He has begun to swim a little more and eat a lot, but still is swollen and mostly stays on bottom. The other koi hides a lot and sometimes stays on the bottom next to him.
Hello, I am Dr. B, a licensed veterinarian and I would like to help you with your wee one today.

If his listlessness improved once the water parameter issues were addressed, it is likely those signs were related to a toxicity with one of the nitrogenous waste products (most likely nitrates). That said, if he has perked up this does hint that the swelling may not be so sinister. Though he may still bottom sit if it is mechanically impeding natural movement.

To give me a better idea of his situation:

Do you think this swelling is a discreet lump or does his back end look distended on the whole?

Any ulcerations, discolorations, redness, or blood vessel patterning in this area?

Have you noticed any change to his stools (ie mucoid, white, etc)?

If possible, could you take a photo of this? If you can do so and post them online, I am happy to have a look (since it will let me see what you are seeing). To post them, you can either use the wee paper clip on the tool bar. Or you can post them on a 3rd party site (ie Flickr, Photobucket, etc) and paste the web address here
Customer: replied 4 years ago.


I can't really assess if it's a discreet lump. The other side does look less swollen today and in the photo I took for you. There are no signs of anything unusual on his body in terms of sores, etc., other than the shape. No pinecone scales, no bulge to his eyes. I haven't notice any unusual stools, but then I don't think I ever notice his stools at all.

Hope these will help:


Hi again,

Now I agree with you that dropsy/internal septicemia wouldn't be expected here (not just because of a lack of pineconing and pop-eye but the fact that we tend to see abdominal distension that doesn't extend as far to the tail). Therefore, when we are considering lumps this far back on the fish's body, we'd be thinking more about superficial tissue layer bacterial infections (causing an abscess), parasite induced muscular cysts, and tumors.

From the first photo you have provided, this does look like a discreet lesion that is underlying the tissues as opposed to growing up from them. Therefore, tumors like lymphocystis (which is virally induced and could arise secondary to the stress this fish experienced) would be less likely.

As well, while this does have an appearance that would fit with muscular cysts, I wouldn't expect this to have necessarily come on in the wake of being poorly kept (I'd be more suspicious if this had developed after the other fish was added if you know what I mean). If we do have muscular cyst formation,t they tends to be due to sporozoa. And in cases of this parasite, we often find that it will spread to other fish and that it is not curable.

That all said, based on his history and the lump's appearance, I'd be most suspicious that this could be bacterial based. If the pond has been in a dire state and this fish has accidentally traumatized this area, secondary infection could have easily resulted. And if this is the underlying cause of his signs, then it would be worth treating him with a course of antibiotics to see if we can at least get a reduction in size if not full resolution. In regards XXXXX XXXXX this, I would that we choose a broad spectrum treatment that will tackle Aeromonas (the most common pathological bacteria in the pond) and to do this we could use a course of oxytetracycline used in combination with oxolinic acid. This does come in a powder form (Koi Fix - link) . Alternatively, I would strongly suggest using either use a feed containing these drugs or even use a medicated feed product like Medikoi (LINK). This will just ensure that we get internal penetration (since there is no external lesion) and this will also minimize the exposure of the biofilter to antibiotics. A typical treatment course would be for 10-14 days.

I hope this information is helpful.

If you need any additional information, do not hesitate to ask!

Dr. B.


Remember that if you have any lingering questions or concerns, please reply so that we may continue our conversation. I will be happy to work with your further and do everything I can to provide you with the service you seek. Please remember to rate my answer when you are satisfied (with4-5 stars or a happy face) so that I may receive credit for my assistance. Thank you & have a great day. : )
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Customer: replied 4 years ago.

Thanks much. Do you recommend the meds in the water or in the feed, considering the other koi now in the pond?

You are very welcome.

Since he is eating and he improved with company (which it'd be a shame to have to isolate him while treating--which we'd have to do if we used water based treatment), I would say in-feed medications would be ideal in this situation. This way you limit the general exposure of the pond's biofilter/good bacteria to the drug and are able to internally treat with the antibiotics to give us the best chance addressing this internalized infection. If you are concerned about dosing around other fish, you could perhaps try to herd him to away from the others to feed or perhaps directly hand feed his medicated feed (it is one of the species where this is a potential option).

All the best,
Dr. B.
Customer: replied 4 years ago.

Thanks very much for your detailed help.



You are very welcome.
I wish you the best with this wee lad.

Take care,
Dr. B.