Well the dreaded day is here ... I have noticed something on one of the koi ...

Here are the best images I could get.

It looks like "Anchor Worm" to me.

Link:
http://www.kokosgoldfish.com/Anchor%20Worm.html

I agree that looks like Anchor worm.




You dont want those in your pond as it is very expensive and time consuming to get rid of them as you have to physically remove them from the infected fish.
Thats why you have to quarintine. Unfortuantly there is No easy treatment for this parasite and with your large pond volume i hate to imagine what the cost is going to be to treat the large water volume to kill larwe or eggs that might be floating around.

Heres one of my articles regarding parasites.

Hi,

from the picture it looks like an anchor worm, and that some infection already started on the tail section that could become an ulcer. Infected area should be clean and friars’ balsam applied.
The best is to catch the Koi and have a better look.

Anchor worms can be remove as shown on the above photo if it is big enough.
Masoten or Dipterex can be used:-
Dip:
10grams per liter water 2-3mins (be very careful - extreme caution)
Bath:
2, 2 grams per 100lt for 1 hour
Pond:
1 gram per 2000 - 3000 lt permanently in ponds
Repeat once weekly for 4 weeks - water temperature 18*C-28*C

Thanx I Didn't Know It Could Swell That Much Now I've Learned Something New.

Thanks guys ... now the question is how the hell do I catch that small fish in such a large pond.

I am seriously considering shooting it with a pellet gun ?

May sound horrific but it is a small fish and I am not too sure I will be able to catch it.

Colyn if there is one there is bound to be more...

Its your choice to destroy the fish or not but that will just be solving the symptom and not the problem....The problem that i am refering to is that your pond might now already contain eggs and killing the one wil not make the problem go away as all your fish could have anchor worms in a week or two if the pond is not treated.

Hi Colyn

I agree that it is anchor worm. If one has anchor worm, the others will also have it. You will have to remove it physically and treat the wound to prevent infection. (I normally clean the wound with hydrogen peroxide, ad malachite green and cover with friars balsam.)

Then you have to treat the whole pond. Trichlorfon or Dimilin works great at 10g / 10 000 liters.

I would also add some Virkon S to lower the bacterial count to try to prevent bacteria going into the wound.

You will have to get yourself a drag net for that pond of yours. You can get it from Allnet.

Dimilin is the best option by far.
Cannot overdose and does not affect the koi at all.
Stay away from Diopterex and Masoten. Very dangerous stuff.

Any luck with the pellet gun idea yet?

Thanks ... where do I get Dimilin ?

Trichlorfon is the active ingredient for Dipterex.
If you want very nervous koi that act like they are the ball in a pinball machine, then use either Trichlorfon or Dipterex.
I have never observed this with any other medication or poison, not even Postasium makes them so nervous and scared.
Should be banned in my opinion.
Lucky for you Paul came to the rescue.