One Koi Keeper's KHV Experience

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One Koi Keeper's KHV Experience

September 22, 2018 - 11:43

Thanks to Monte McQuade, our own Show Water Quality instructor, for sharing his heartbreaking experience.

How did it happen?

Knowing how KHV works:  It is not always the first fish to die that is the infected or carrier.  With that in mind:  I had removed 7 fish from my QT/grow out tank (1800 gallons) that I had been growing in it for the last year.  This was in anticipation of adding another batch of smaller fish that I had coming in.  These new fish came from two sources.  Within 3 days the fish from one source became lethargic and all three of these fish died the first week.  Then the new fish from the other source started swimming with erratic behavior and became lethargic.  One at a time over the following week these fish began to pass.  The next fish was the last of four fish from the first source but had come from another tank at that vendor.  In short all but one of the new fish died within two weeks.  No established fish in the QT/grow out tank died the first two weeks.

There was a pause and I began losing fish that had been in the QT for a couple of months.  Then longer established fish (up to 1.5 years) began to die in this system.  My QT is used more as a grow-out tank and I had fish in it from probably five "importers" and various farms.  The system has been running for about 3.5 years and has never been sterilized between groups of fish.  When a fish goes in, it is in the QT for many months while it grows.  Usually through the Winter for sure.  I had also stopped the practice of "keeping" a rescue fish from when my club rescue's a pond the previous year.  The only other piece to the puzzle is that the temperature was raised in the QT from the low 70's (68* to 72*) up to 74*F in anticipation of starting to grow the new fish. 

History in the QT/ grow out system:

Some occasional deaths due to visible disease process.

High number of fish with massive amounts of filtration and aeration.  Less fish/biomass than a dealer's stocking level would be in an 1800 gallon system.

7 - 18" fish removed to outdoor pond the week prior to adding new fish.  8 New fish were added 6-13”.

Several days prior to the larger fish being moved to the outdoor pond.  This system was treated with PP, Proform-C and Prazi both to clean those fish and the tank for the new incoming fish.

Approximately a 5%+ water flow-through each day. 365 days a year.

Injured fish were healing during the entire KHV outbreak period.  Two of these injured fish were still alive during depopulation of the system.

The fish submitted for KHV testing were all long occupants of the QT system.  As the new additions had passed and were no longer available to be tested.

Fish were also submitted from each of my other ponds.  Results varied but all were positive for KHV and various bacteria's.

Only one fish survived of the new fish added to the QT.  So of course it must be the carrier!  Not true.  This fish was in a system at the vendors before being picked up for well over a month after it had arrived from Japan.  No deaths have been reported back to that system.  Three of my fish’s deaths came out of that same tank and were healthy for over a week to ten days prior to their passing within the QT.  So I doubt that that fish was a carrier but naturally immune and would had become a carrier within my QT.  Ultimately many fish survived several days beyond the last death in the QT and the system was depopulated after approximately 6 weeks.  There was about a 60% mortality rate from the dieses. 

One outdoor pond was also depopulated after fish began dying approximately three weeks after initial onset of symptoms within the QT and the KHV testing results were in showing this pond as being positive.  This I blame upon myself.   I have nets and bowls for the QT separate from the ponds.  But I would often clean all the sieves for all my ponds at the same time.  I also feed all the ponds while I am out there.  So I believe that I was the carrier to the other two ponds on the property. I did not wash or alcohol my hands between cleaning these systems. I doubt it was a splash within the filter house between systems.  At this time KHV has not been shown to be able to be transferred via the air. 

My lessons learned:

If you are going to have a QT then it must truly be treated as a QT and not a grow tank.

It must be located away from other systems so human transfer cannot take place much less equipment crossover or splashing.

Daily take care of the healthy fish first AND THEN the cute babies in the QT.  I always did this in reverse to my shame.

In closing:  I had become very casual of my care of my ponds.  Had I followed all the proper protocols for a QT system.  I should have caught this before I spread it throughout the other two ponds.  I would have lost the fish in the grow out system, but I could have still had my other fish.  Because I had become lax, I now have some decisions to make: 

I have depopulated two of my four ponds.  Do I put all my fish down based upon the results I have received?  Do I wait on my large fish pond and watch it with retesting?  The large fish pond's KHV test was on the borderline of the parameters and I have had no deaths in that system.  The fourth pond was populated while this was happening and in theory is not positive.  At this time I am not sure what I will do.  I am not sure where I will be in the hobby in the future but it will certainly not be at the level I was at this year.  It has taken me over a decade to get the size and quality of fish that I had.  I will retest the last two ponds this month and see where that will lead me.  Had I followed all the proper protocols for a QT system,  I should have caught this before I spread it throughout the other two ponds.  I would have lost the fish in the grow out system, but I could have still had my other fish.  Because I have become lax I now may have none.


!If you're not havin' FUN, you're not doin' it right