koi flashing

[Jenny]

So this same thing happened last year and I never figured out what was wrong and ended up losing 2 fish. There was flashing followed by eventual lethargy at the surface. The flashing has started again this year....what should I do? Should I just do a big water change and a broad spectrum treatment like microbe-lift?

 

[Jenny]

Additional info: 5000 gallons filled about halfway. Has 2 koi that are about 2 feet, 1 that is about 7 inches. Many that are fingerlings. Ammonia 0ppm. About to check other parameters.

 

[Meyer Jordan]

A water change is the last thing that you want to do. 'Flashing' is usually (but not always) a sign of an irritated fish. It may be due to parasites, high ammonia or Nitrite or any other source of irritation to the fish. The fish are already stressed and adding more stress through a water change will do more harm than good. Unless you have the use of a microscope and can do scrapings, you will have to rely on what can be observed with the naked eye. Do the fish have any unusual spots or bumps? Is the skin discolored? Do the fish appear to be breathing faster? Any other unusual behavior besides 'flashing'?

 

[Jenny]

But in order to use a broad-spectrum treatment, it says start with a 25% water change....

And the only other thing I see is that yesterday, the male was hanging somewhat close to the surface. A few inches down. Not gasping or anything, but definitely lethargic. Just a couple of days ago they were being completely normal.

 

[Jenny]

Please help guys...I can't lose these fish.

 

[Meyer Jordan]

Why is the pond only filled halfway?

 

[Jenny]

It's an aboveground tub/pool and the filter is inside of it, placed on cement blocks. The water level comes up right under the output of the filter. I could raise the filter with more blocks and fill the pool more, but it's already about 2500 to 3000 gallons, so I figure it's unnecessary.

 

[Jenny]

I believe last year it was gill flukes. Should I start with a treatment for gill flukes if all of my parameters check out?

 

[Meyer Jordan]

Can you net one of the affected fish and give it a closer visual examination?

Also, are any of the smaller fish and/or fingerlings showing strange behavior?
Have you recently added anything to the pond?

 

[Jenny]

Wouldn't that stress it out more? Also I think it'd be difficult to net them....

 

[Meyer Jordan]

Wouldn't that stress it out more? Also I think it'd be difficult to net them....

Will a doctor prescribe any medication without seeing the patient first? Using the wrong treatment can cause further harm.

 

[Jenny]

But it's recommended to use fluke meds every spring and fall anyway, regardless of whether symptoms are observed

 

[Meyer Jordan]

But it's recommended to use fluke meds every spring and fall anyway, regardless of whether symptoms are observed

Recommended by who? The treatment manufacturer?

 

[Jenny]

Every site I've ever seen says to always treat for flukes in spring and fall.

 

[Meyer Jordan]

http://www.tetra-fish.com/aquarium-information/aquarium-fish-diseases-how-to-spot-them.aspx

http://www.fishvet.com/Flukes.htm

You will notice at the second linked site that 'flashing' is not mentioned as a sign of flukes.