2nd April 2000: The client phoned to say that over the
last few weeks he had lost 9 koi. The fish that were left looked unhappy
and one had a "lump" on its side.
(I think you will agree it wasn't a lot to go
on! Yet plenty of people would have been prepared to make a diagnosis
and suggest treatment plans on this scrap of information).
The pond was a 20,000 litres (4,500 gal. UK) rectangular koi pond
with a Cloverleaf filtration system.. The pond had extensive areas of
frothy foam over the surface. The fish were nervous, several had
reddening on the body and fins, some had fin rot and one had a severe
swelling on its side with clearly visible raised scales.
The owner told me that six weeks ago somebody had been to see the
fish, and after looking into the pond had announced that the fish had "mouth fungus" - sold the owner
some treatment and left. Since that time fish had been slowly dying,
with a total loss of 9 koi over the six-week period.
Water tests showed a raised ammonia level (0.1 mg/litre) and a high
nitrite level (1.0 mg/litre). This was traced back to the fact that the
pond hadn't been topped up for a while and the water level in the filter
was only just above the chamber weirs - consequently there was
hardly any water passing through the filter. In essence there was hardly
any filtration taking place - luckily it wasn't summer-time when the
build-up of nitrogenous wastes would have been even higher.
The filter had not been cleaned out for some time and was clogged
with rotting organic matter - because the owner
had been advised never to clean it.
A skin scrape of two fish showed very high levels of white spot;
indeed the slide was alive with them. There was also Chilodonella
present and I found a couple of fish lice on the fins. The koi
with the "lump" was a mess when we took it out the water - the
owner was shocked.
[It is important to realise that viewing the
fish in water does tend to mask the degree of damage. This is why fish
need to be examined out of the water]
There was an extensive area of swelling from the anus reaching
forward to just before the pectoral fin. The scales were raised, with a
large central area that was bloody and infected. There was also
extensive fin erosion and indications that the bacterial infection had
become systemic. I suggested to the owner that the fish should be
euthanased, but he asked for it to be treated with antibiotics. I did
treat it but its condition deteriorated and it had to eventually be put
to sleep with an overdose of anaesthetic.
All treatments were complicated because the water temperature
was only 80C, making treatment of any secondary
bacterial infections difficult. Low water temperatures will also slow
down the life cycle of both white spot and Argulus. For example,
the life cycle of white spot can be four weeks or longer at these
low temperatures. The problem being that the white spot parasites can't
be killed until they reach the free-swimming stage of the cycle.
I judged the white spot to be the main problem and the pond is now
being treated with malachite green and formalin every 5-6 days. The
frequency will be increased as temperatures warm up.
Once this problem has been resolved (hopefully within the next 5-10
days now the water is warming up) an assessment will be made
regarding the necessity of other treatments. One koi seemed to be
affected more than the others. He had pink rather than white skin as
well as frayed fins - a typical sign of severe stress. A close
examination showed that he was covered in characteristic white spots. He
was taken away and put in a heated treatment tank to speed things up.
After just a couple of days in M&F he is looking much brighter.
Hopefully there will not be any secondary problems.
Up to date
06/04/00: The pond has now had two treatments (M&F) -
there have been no further losses. With a change of weather and warmer
temperatures hopefully the next week or so will see an improvement.
Update 12/04/00: No further losses. Fish examined and skin
scrape taken. No sign of parasites. Pond re-treated with M&F. Client
advised to obtain some masoten to treat lice as water warms up. There
doesn't appear to be any secondary bacterial problems at present.
Because of the cold weather and a slower life cycle it is not possible
to say for certain that the white spot has been eliminated, so a
follow-up examination will be done in 2-3 weeks
Update 28/04/00: A follow-up examination showed
that the white spot has been eliminated. The client has obtained some
masoten and 2 treatments have been given. There is no sign of fish lice
and there have been no further fish losses. A small amount of Trichodina
was found and this will be treated in the next week or two. The fish
that was taken away has been returned looking the picture of health.
Clearly, the cause of the original losses was a misdiagnosis or more
accurately a wrong guess. What started with a simple parasite problem
has now been complicated by secondary problems.
These problems have been complicated by failure to maintain the
system and make sure the filter was working properly. The spread of the
disease has also been helped by typical British spring-time weather with
The low water temperatures have meant modifying the treatment regime
to take account of the extended life cycle of the white spot parasite - a calculation that could not have been made without a
skin scrape to actually identify if and what sort of parasites were
Once a proper examination was carried out the problems were easy to
deal with. However, if a guess had been made and a couple of random
treatments used there is every possibility that there would have been
further losses and complications in the weeks to come.