Unexplained Koi Deaths

[amy1994]

We have recently got 3 small koi from our lfs, there our others in the same holding tank but from a different place.
2 have died within the last 2days, and the last 1 of the 3 swims for a bit then floats for a few minutes and starts swimming again.
We have also come in occasionally and seen him floating on the top, we thought that it was dead, but then it started swimming again...
Does anyone know what is wrong with him?
Was wondering if there was something in the water in our lfs, as only those 3 seem to be affected, will it affect the other fish?

 

[nurglespuss]

Poor quality or diseased fish, I would remove the ill fish

 

[amy1994]

Poor quality or diseased fish, I would remove the ill fish

Unfortunately all 3 are gone now
And all of the other fish which were with them are fine, must have something with them from before..

 

[Tokis-Phoenix]

Water quality problems are a common cause of death & disease in fish. Though the fish are dead now, if there was a particular reason for it its important not to repeat the same mistake when buying new fish. Fishes tolerance of water quality problems varies from fish to fish.
Pet shop aquariums are also often rife with fish disease's & parasites as many LFS aquariums are run off the same filtration system, and with fish arriving stressed & hungry every week and then put into overstocked tanks, diseases & parasites can spread like wildfire.

When putting them in the holding tank, how large was it and was it filtered? Even quarentine tanks need to be cycled (put through the process of the nitrogen cycle) as as soon as you put fish in it (ammonia source) this will trigger the nitrogen cycle, causing very unstable water quality which can finish the fish off. And even though the tank is only a quarentine tank and not a permanent home, it still needs to be a certain size.

Another thing is that the fish may have already been sick to begin with. When choosing fish you should look out for these symptoms;

Underweight or concaved belly- sign of internal parasites/bacteria.
Red/inflamed gills - sign of gill flukes
White sand sized spots- whitespot/ich parasite
Dusty gold covering on fish- velvet parasite
White stringy looking poop- sign of internal bacterial or parasite infection
Hanging around the surface a lot, rapid breathing- sign of gill flukes
White/grey slimey or slight fluffy patches on fish (particularly on the "saddle" area of the fish)- bacterial columnaris infection
White fiberous fluffy growths- fish fungus
Bent spine/warped body- fish TB
Random patches of colour missing from fish or warped body etc- neon tetra disease (not exclusive to neon tetras btw)
Red bloody streaks or patches on fish (whether on fins or body)- septicemia/internal bacterial infection
Tattered, eroded or nipped looking fins- finrot
Lethargic behavior- internal bacterial infection or begging of another infection
Inflamed/red anus- internal parasites

Etc.

Pre-research is very important not only so you know how to look after your fish properly (and more importantly that you have the means to look after them properly) but also so you can familiarise yourself with what a healthy specimen of the fish in question should look & behave like . Fish don't die for no reason at all, there is a reason for everything, so figuring out the likely cause of death is still important for preventing future mistakes etc .

 

[amy1994]

It has a normal sponge filter, powered by an air pump, the quarentine tank is 500-600l, it is big.
We do water changes regularly, i had looked on the internet for what sort of diseases, i looked over the 3 koi as they were about 3-4 inch, but there wasn't a physical sign of anything wrong.
When we first bought them, the tanks they were in were pretty dark, but they weren't acting unusual.
They were british koi.

 

[Tokis-Phoenix]

Hmm thats odd- when you acclimatised them to the tank, how long did you acclimatise them for and how did you go about it? Do you know if the place they originally came from have a PH similar to that of the tank? Is there the possibility that any contaminants may have gotten into the tank (cleaning chemicals, deodorant etc)?

 

[amy1994]

Hmm thats odd- when you acclimatised them to the tank, how long did you acclimatise them for and how did you go about it? Do you know if the place they originally came from have a PH similar to that of the tank? Is there the possibility that any contaminants may have gotten into the tank (cleaning chemicals, deodorant etc)?

No meds have been put in to the tank, and as we have it in a seperate room where nobody normally goes, it is sealed off so no animals or anything can get in there, we only go in there if we need to change the water/clean/feed or just to look at them. The room isn't really used otherwise.
There are still a few koi in there now, and they are fine, we have checked them over for any physical signs, and they are acting normal and eating fine.
When we acclimatised them, they were in the bag for a while, i can't really remember how long for but i know it was for a pretty long time.
We made sure that the temp was the same, and then we started adding little bits of the quarentine tanks water in to the bag, and after a while let them in, and they looked fine.
The LFS that we got them from i honestly don't know, they just said that they should be fine as long as obviously we acclimatise them.
We have always used different nets/gravel cleaners etc for the koi, so nothing gets passed over from our other tanks, and i know they weren't mixed over.

 

[Tokis-Phoenix]

Hmm well internal bacterial infection can be a cause for sudden unexplained deaths. But there may also have just been an issue with the quality of fish themselves- you say you got them from a separate placee and its only the koi from this place that died? Do you know how long they were at this place before you bought them? If the fish only arrived at the place the same day you bought them they could have already been very physically stressed and one more move was all it took to finish them off.

 

[amy1994]

Hmm well internal bacterial infection can be a cause for sudden unexplained deaths. But there may also have just been an issue with the quality of fish themselves- you say you got them from a separate placee and its only the koi from this place that died? Do you know how long they were at this place before you bought them? If the fish only arrived at the place the same day you bought them they could have already been very physically stressed and one more move was all it took to finish them off.

Yes it is only the 3 fish i got from the LFS that had died. The other koi are from different places.
I don't know, but i would be surprised if the sold on the same day, as they have never done this with their other fish, they always have the little sign saying 'recovering from journey'.
I also don't know how long they had been there beforehand, they weren't very big though only 3-4inch.

 

[Tokis-Phoenix]

Some LFS sell fish on the same day of arrival- bad practice, but a surprising amount do it. The longer a fish has had to rest at the petshop the better its chances of survival being re-moved and acclimatised to a new tank.
But if the LFS usually doesn't sell fish on the same day of arrival then that would rule this out. But the fact that all were dead within a week of being in the tank while the others survived, leads me to believe that whatever the case they were not in good physical health before they were even bought. A healthy fish which has been properly acclimatised to a suitable tank which is free of water quality problems etc should not die within just a couple of days.

So right now i would put my money on something like an internal bacterial infection being the cause of death. Personally i would treat the tank with an anti internal bacterial medication as a precautionary measure as when fish die in tanks this is the prime time for disease to infect other fish as it leaves its old hosts body. Other than that, i would just advise keeping a very close eye on the remaining fish (particularly for symptoms of bacterial infections like white stringy looking poop, lethargy, skinnyness, paleness etc) .

 

[amy1994]

Some LFS sell fish on the same day of arrival- bad practice, but a surprising amount do it. The longer a fish has had to rest at the petshop the better its chances of survival being re-moved and acclimatised to a new tank.
But if the LFS usually doesn't sell fish on the same day of arrival then that would rule this out. But the fact that all were dead within a week of being in the tank while the others survived, leads me to believe that whatever the case they were not in good physical health before they were even bought. A healthy fish which has been properly acclimatised to a suitable tank which is free of water quality problems etc should not die within just a couple of days.

So right now i would put my money on something like an internal bacterial infection being the cause of death. Personally i would treat the tank with an anti internal bacterial medication as a precautionary measure as when fish die in tanks this is the prime time for disease to infect other fish as it leaves its old hosts body. Other than that, i would just advise keeping a very close eye on the remaining fish (particularly for symptoms of bacterial infections like white stringy looking poop, lethargy, skinnyness, paleness etc) .

Okay, thanks for all your help, i will definitely do this as don't want anything happening to the others