Fish disease treatments are often the main threat
Often the biggest threat to koi health are fish disease treatments!
How do most disease treatments work? Should you treat the pond or the
fish? Whatever you do take precautions.
There are several considerations when using a pond 'medication' but
undoubtedly the most basic is to understand their true nature. Pond
treatments are often referred to as 'fish medications', a misleading
term. With few exceptions the most commonly used treatments are not
medications in the accepted meaning of the word - that is, compounds
specifically formulated to be used in the treatment of disease.
Most chemicals used for fish treatment are toxic, taken straight from
the chemist's laboratory and normally used for other purposes. They work
as 'fish medications' simply because they are potentially toxic to all
forms of life, but tend to kill the smaller organisms, such as fish
parasites, before the larger ones, such as koi!
If we get the dosage right then we can kill micro-organisms such as
parasites and bacteria before doing any serious damage to larger
animals, such as koi. However, I should stress that often the borderline between safety and toxicity is very small and
every year thousands of fish die as a direct consequence of chemical
overdosing. Because of the way that these chemicals work it is virtually
impossible to reverse the effects of overdosing, the exception being
salt, which works in a different way.
If my comments above have changed your perception of chemical
treatments then the most important lesson has already been learned. When
administering chemical treatments to the pond it is important to realise
beforehand the potentially devastating effects if you get it wrong.
Respect and caution are the golden rules to observe when handling the
potentially dangerous chemicals that many 'fish medications' are.
Treat the pond or fish
The first decision is whether to treat the pond or the individual
sick fish. Unfortunately, there are no hard and fast rules, it depends
on the circumstances. In general, treatment of an individual fish is to
be preferred. This is particularly true where bacterial, fungal or gill
problems are suspected. But where there is a generalized parasite
problem, pond treatment is preferable, in order to treat the various
stages of parasite development and reduce the overall parasite
This obviously presumes that any remedial action has already been
taken to isolate and correct any environmental or other stressors
responsible for the underlying problem. Using treatments without
correction of underlying problems is simply a waste of time, usually
resulting in yet more stress for the fish and further health problems.
If just one or two fish are affected, then it is probably better to
treat just those fish in a tank or a bath, returning them to the pond
after treatment. If a succession of treatments is required, then the
affected fish can either be permanently isolated in a separate tank or
returned to the main pond between treatments. Individual treatment has
several advantages in that any treatments can be better controlled and
the fish more easily removed if it reacts badly. It is also cheaper in
terms of chemical costs and it avoids the risk of upsetting the delicate
eco-balance established in the pond and filter.
The use of a short-term bath also enables higher, and therefore often
more effective doses to be given. If fish are to be removed for
longer-term treatment, e.g. where there are bacterial
problems, then a suitable quarantine tank of adequate size is an
essential requirement. Trying to treat fish in a small, badly designed
tank is pointless, as any beneficial effects will be quickly negated by
the stress caused by such poor environmental conditions.
When handling any chemicals, always wear gloves. As already
mentioned, some chemicals are poisonous and may irritate the skin. Mix
the required amount in a bucket or similar, to ensure that it is fully
dissolved. This is particularly important with tank treatments as uneven
mixing could result in areas of high chemical concentration and
therefore higher toxicity.
Always aerate tanks while treatments are in progress; cover the
treatment tank to prevent fish leaping out and NEVER, EVER leave
the tank during the initial stages of treatment. Bear in mind that you
are dealing with a sick fish that may not be able to stand up to the
treatment or alternatively the diagnosis may be wrong and the treatment
may exacerbate the problem.
It is important that treated fish are watched immediately following
treatment. Have a tank of clean, aerated water to hand in case a fish
reacts badly. On a practical note, a sock-net is invaluable for
transferring fish between pond and tank. These nets remove the risk of
dropped fish, making handling less stressful for both fish and handler.
When the treatment time is complete, ideally the fish should be returned
to a tank of clean water, rather than being put straight into the pond
-this enables the keeper to monitor its progress and check that the fish
is recovering well.
Isolate the filter
Pond treatments, if they are to be administered with minimal risk,
need careful thought and preparation. The first consideration is the
filter system. I have heard it said that chemicals attack only
'bad' bugs and have no effect on 'friendly' bugs. A moment's thought
suggests that this is highly improbable. The general undiscriminating
nature of these chemicals means that both good and bad bugs are likely
to be killed so, ideally, the filter should be isolated while the pond
is being treated. How easy this is in practice will obviously vary from
system to system. In the conventional gravity-fed filter it is
relatively easy to block off water feeds and returns and set up a small
pump to continue to circulate the water within the filter. In this way a
filter can be isolated from the pond, for days if necessary. Koi-keepers
using other types of filter system may not find it quite so easy to both
isolate and keep a filter running.
I am thinking of box-type filters in particular, where it is
impossible to continue to circulate water in isolation from the pond.
Even with this type of system, however, it is still possible to isolate
the filter for some time without having an adverse effect on filter
activity. Provided that the media are kept submerged by either plugging
the water return or removing the media to a large tank filled with pond
water, the filter bacteria will remain viable for a considerable time. A
couple of air-stones under the media will give some water circulation as
well as ensuring a continuing oxygen supply.
How long a filter needs to be isolated depends on the type of
treatment used and how quickly it breaks down. I would suggest a period
of several hours, say, overnight. Obviously, if the filter is isolated,
and therefore water returns switched off, supplementary aeration is
vital. Any additional aeration needs to be quite heavy, as some chemical
treatments, particularly those containing formalin, remove oxygen from
the water. A Hi-Blow air pump is ideal for this
A good clean
Another simple precaution before dispensing a treatment is to give
the pond a good clean, getting muck and waste off the bottom. I can
sense a few puzzled looks at this piece of advice but a little thought
shows that it makes good sense. Many chemicals used for pond treatment
will react with organic matter such as fish waste and detritus. Giving
the pond a clean before treatment ensures that more of the chemical is
available for therapeutic use rather than simply being wasted in
unwanted chemical reactions. This is particularly important with
potassium permanganate, which can be rendered useless in a dirty pond. A
clean pond also reduces the risk of water quality problems while
treatment is in progress, particularly if the filter has been isolated.