Koi - anyone know how to help a seemingly sick fish?

[Earlybird]

Just went out to feed the fish, and the largest koi is moving very slowly. Wasn't interested in food, and seems to be listing ever so slightly to one side. For a time was moving slowly along the surface of the water seemingly 'gasping', but now has moved down deeper.

Can I do anything to help it?

And if it is relevant, the only thing that has changed recently is we added 5 much smaller fish to the pond about 10 days ago (not koi) from a reputable shop who has supplied all our fish in the past.

Have you checked the water quality? Has he any other symptoms? Any marks or bulges or anything?

Hopefully one of the new fish hasn't brought anything in. New fish should always be quarantined, even from a good shop because the livestock turnover means that they can't guarantee that every fish is 100% healthy.

Could it be a swim bladder problem? My diamond sturgeon had this and listed markedly to the right.

Is it the same as tank fish where adding the 5 new fish will overload the water chemistry with additional waste? Possibly made worse as the water levels may already be low with the weather..

Can you check the water like you do a tank? Add some fresh water?

Yes, could be a swim bladder problem. There are quite a few different things that can affect the swim bladder.

Thanks for replies.

I gave the filter an extra good clean, added more water and dechlorinator (we are not in the UK), and am hoping that will solve the issue.

If the fish has a swim bladder problem, is there anything that can be done?

How did you clean the filter?

'Swim bladder' is a symptom, not an illness in itself. It can have a number of causes so it depends on what's causing it whether it can be fixed. You're not in Germany or the Netherlands by any chance, are you? Those countries are well ahead of the curve when it comes to aquatics so if you're there then you should be able to find a vet that deals with fish.

Nope, am in America.

I cleaned the filter by giving it a good rinse on both sides with a high pressure garden hose.

I can take a sample of water into the fish store for testing, but wonder how much that will help. All the other (smaller) fish are darting around as normal - no symptoms.

The big one has not eaten for 2 days.

Ah, OK. You might be able to find a fish vet in the US, especially for a koi because some of them are very expensive so seen as worth spending the money on.

Don't use tap water to clean the filter again. It's less important in a pond because the stocking level is lower than that of an aquarium, but the chlorine in tap water kills off all the good bacteria in the filter so can raise the ammonia level.

I'd get the water tested just in case. Have you had any thunderstorms lately?

No thunderstorms for at least 2 weeks, so don't think that is the issue.

And you are right, the chlorine is not good for the fish - hence the declorinator that is added into the water. There is no other water source here.

I've just been out to look again. The big one is very lethargic/listless, and the little ones are darting about as normal.

So the water from the hose doesn't have chlorine in? That's OK then. Filters should always be washed in dechlorinated water.

Sounds like it could be a either a bacterial infection or an internal parasite. There's no way to tell really but there are some treatments you could try. I don't suppose there's anywhere you could isolate him? If not, you could try a gentle treatment like Melafix or food with added garlic. That wouldn't harm any of the healthy fish.

Sorry if I have been unclear: all tap water and garden water here is chlorinated. There is no way 'round using it. So, we use it and then put a dechlorinator in the water - which I am told acts almost immediately. So the fish are not subjected to chlorine for any length of time.

The filter is washed with this same water, but is quickly immersed in the dechlorinated water shortly after we add in the tablets.

That is the method we have been using with our fish ever since we got them (6 years ago), and they have been fine.

We did briefly consider isolating the koi, but though we have a suitable container, we have no way of getting oxygen into that water on a regular basis.

In spite of all our efforts, I think our big koi is not going to make it. Such a shame.

Thanks for all your advice.

It's not the fish I was worried about- the filter is home to a lot of bacteria that help to process fish waste. The chlorine will kill them so you should only ever clean the filter with dechlorinated water. Again, it's less important with a pond than with an aquarium because the stocking level is lower, but it may still cause spikes in the ammonia level which over time will weaken fish.

Really sorry about your big koi. Is there an aquatic store nearby that sells medicated food or some of the less drastic pond treatments?

To clean the filter sponges take a bucket of water from the pond and rinse them in that with your hands, that will avoid any chlorine.

As for the fish it could be lack of oxygen in the water or an imbalance, it's noticed faster by larger fish. You can change some of the water to give them fresh, about 20%. You can also put the fish into a large net that will hold it in the correct position in the water then move it through the water to help more pass through the gills and therefore give more oxygen. I suggest also a careful glance at the gills, they need to be deep red, anything else would suggest a problem.

Thanks for advice.

Sadly, the big koi did not make it. All the other fish seem to be fine. Am watching closely though.