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 (Koi Health)
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A new Koi Health section is currently being written and will be here as soon as time permits. As it evolves, it will be organised into suitable categories, but until then, this is what I have written so far.
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General Principles
Koi health problems, an introduction
I don’t keep Cod, I keep Koi
Why is it necessary to repeat the dose of pond treatments when treating for parasites?
Should filters be turned off during treatments?
Why is it necessary to increase aeration when treatments are added to a pond?
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Koi health problems, an introduction.
The intention of this page is to provide advice for those whose lack of experience leaves them feeling “out of their depth” in the face of what sometimes seems to be an information overload of confusing and sometimes seemingly contradictory advice. Externally visible wounds, sores and infections are fairly easy to diagnose, even for the inexperienced pond keeper. But in the absence of externally visible problems, how do you determine if there actually is a health problem and how do you begin to tackle it? It is difficult to diagnose sick fish without the benefit of seeing them, but general good advice is as follows.
Remember, we don’t keep fish, we keep water. This expression cannot be repeated too often. Koi are living creatures with an immune system that tries to keep them healthy. In good water, this system will usually be fairly successful. One part of a fish’s self defence system is a mucus layer which covers the skin and scales. It contains antiseptic chemicals and antibodies. It is continuously renewed from cells within the skin, and it’s purpose is to kill invading organisms, or at least slough them off with the excess mucus that washes off the fish as new mucus is produced underneath it. Beyond this mucus layer is the immune system itself. This is very efficient at fighting off normal levels of the invading organisms that commonly share the fish’s environment, but it can be suppressed when the fish is under stress. If the Koi is very stressed, the immune system can be almost totally ineffective. In bad water, the fish will be stressed. Their immune response will be less effective and the Koi will be at risk of contracting a disease that they would otherwise have been able to resist. There are similarities with the human immune system. Your mum was right! If you spend a day playing in the snow without being wrapped up warm, you will catch cold. Snow does not contain the Rhinovirus (common cold germ) but by exposing your body to extreme cold conditions you will lower your immune system. The Rhinovirus, to which we are continually exposed, and which is normally resisted, will seize the opportunity and multiply in us, causing the runny nose etc. that we associate with catching a cold. Fish are exactly the same. If poor conditions stop their immune system from resisting infections, they will succumb.
If a fish behaves unusually and there is no obvious external reason, do not immediately rush for the net and start examining it. A sick fish does not need extra stress. It may be necessary to examine it later but this should be a last resort, not first.
Do not guess what the problem could be and bung in a treatment “just in case”. The chances of correctly guessing are outweighed by the chances of doing more harm than good.
Do thoroughly check your water parameters, and take any corrective action without delay. Gasping at the surface may well be a symptom of a parasite infection or it may simply be that the water is not well aerated. Either way, the chances of a full recovery from a parasite infection are reduced if the water quality is poor. Get the water to an acceptable standard first and then see if the fish spontaneously get better or still exhibit the same symptoms.
Get expert advice. “Proper” Koi dealers usually have sufficient knowledge to correctly diagnose problems and advise the correct course of action. Avoid advice from garden centres or the pet shop that specialises in flop eared rabbits, and a few Koi as well, unless you know that the person also happens to be an experienced Koi keeper. If you are already a member of your local club, you will know who to ask. If you are not a club member, contact your local club and ask them for advice. You may be referred to someone who is prepared to help you now, and maybe even come round to look, but on the strict understanding that you will join that club at the next opportunity. All clubs are on the lookout for new members, and if you can get prompt help in exchange for joining a club (and learning even more), that’s not a bad trade.
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I don’t keep Cod, I keep Koi.
If Koi, or the Carp from which they have been bred, preferred salt water, they would have packed their bags and moved from their lakes to the sea many thousands of years ago. Or to put it a little more seriously: All living creatures have evolved to exactly suit the environment in which they live. Fish in salt water have evolved to do best in salt water, fish in fresh water have evolved to do best in fresh water. We tamper with that arrangement at our peril, or more exactly at the fish’s peril.
In a recent thread on KoiChat, (click to see the thread), one of the contributors to the thread included a long article from Duncan Griffiths that advised against the use of salt as a pond treatment. Having previously read the article, I agree with every word, but it’s sheer length may deter many Koi keepers from reading the valuable information within it.
Salt is an excellent treatment for a range of Koi ailments but it should be kept as a treatment and not used as a continuous additive to the pond. My view on the same subject is, (I think), a little simpler: Read this, then if you want to read Duncan’s more detailed article, click the link below.
External wounds
Fish have a skin which is designed to keep water out and their body fluids in. If the skin of a fresh water fish is damaged, or if it is breached by an ulcer, what happens is that water can get into the fish and dilute its body fluids to the point that they would no longer function. The fish would die. This process is called Osmosis. The osmoregulatory system of Koi will be covered in much more detail as this section evolves, but in essence, Osmosis works like this:
Water always tries to move from lower concentrations of chemicals to higher concentrations. It will do this until the higher one has been diluted to the same degree as the lower. Fresh water fish have a much higher concentration of chemistry inside them than in the water outside. A fresh water fish with a damaged skin will find that water is entering it through this wound. The kidney will work overtime and will expel as much of the excess water as possible by increasing the rate at which urine is expelled. If the wound is minor, it will successfully do this until the wound heals and the ingress of water stops. If the wound is more serious, the kidney may be damaged by having to work too hard, leading to additional health problems, or it may be unable to expel water quickly enough and the fish will be “diluted to death”.
Exactly the opposite happens if a salt water fish has a damaged skin. The concentration of chemistry inside it is much lower than in the sea water outside. If a salt water fish has it’s skin damaged, water will flow out of it until it has diluted the sea outside to the same level. Clearly this cannot happen, there is not enough water inside a fish to dilute the sea. So the fish will die of dehydration in the process.
There is a balance point. If a fresh water fish is placed in a hospital tank and salt is added so that the concentration of salt outside the fish is the same as the concentration inside it, then water neither flows in nor out. The wound can then heal in peace without the kidney having to try to work harder than normal. A salty environment is good for a fresh water fish while it has damaged skin.
Parasite Control
Higher concentrations of salt in a hospital tank can kill some parasites. (Look on treatment charts to see which ones. A treatment chart will appear here in due course). The way they are killed is like this: Remember that water flows from lower concentrations to higher. If a fresh water fish that is affected by parasites is put into a short term bath with a high concentration a of salt, then water will be drawn from inside the parasite to the higher concentration outside. This means that the parasite will dehydrate very quickly, Literally, death within a few minutes is possible. At the same time, the fish is also dehydrating by the same process, but because of it’s much larger size it would, if left in the bath, take longer to die. The trick is to leave the fish in the bath just long enough to kill the parasites, but remove it before it suffers any lasting damage. A short term salt bath is effective at killing some parasites provided the fish is watched carefully and it is removed if it should show any sign of distress.
Stress
It is impossible to tell whether a Koi is thinking happy thoughts or not, but by general observation of it’s behaviour, it can be seen that if a stressed fish is placed in a hospital tank and salt is added, the signs of stress will reduce.
Mucus
For a fish, the first line of defence against parasites is the mucus layer. It contains antibodies and chemicals that are designed to kill invading organisms. It is continuously produced by cells in the skin. As new mucus is produced, the old mucus is sloughed off. This will also help remove any parasite that is trying to invade. Mucus production increases as a natural reflex action of the immune system when it is under attack from invading organisms. Salt will also trigger this reflex action and cause the mucus layer to thicken. This is another example of how salt can be used to help control a parasite attack.
If salt works so well, why not add it to the pond as a continuous preventative treatment?
It’s not as simple as that. If I have a headache, I take two Paracetamol. The headache goes away. Paracetamol “cures” a headache. However, this is not a good enough reason to take eight Paracetamol per day, every day, in order to prevent future headaches. Too many Paracetamol can do more harm than good. Similarly salt can be used to “cure” some fish problems, but in doing so it is messing around with their osmoregulatory system and their immune system. This is acceptable for short periods in order to help cure them of an ailment, but it is far better to give them good quality water so that their immune system functions well and keeps them healthy as nature and evolution intended.
To read what Duncan has written about salt in much greater detail, click below.
http://www.koiquest.co.uk/salt%20but%20no%20vinegar%201111.htm
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Why is it necessary to repeat the dose when treating a pond with medication for parasites and is timing important?
Some parasites reproduce either by laying eggs on surfaces in a pond or by scattering eggs into the water. The reason for repeat dosing a pond with medication when treating for these parasites is because, although they can be killed whilst they are in the free-swimming adult stage, the treatment is usually ineffective against unhatched eggs. The first treatment will kill the adults, but then a few days later, any eggs will hatch. At this point, the original treatment may be too weak to have any effect against them. So the second treatment is to kill the new generation of free-swimming adults. The third treatment, if recommended, is "insurance" against any late hatching eggs.
The timing of the second or subsequent doses is important. If the treatment is too soon after the previous dose, there is the possibility that the eggs will not have had time to hatch and the new generation will still be protected inside these eggs. When they subsequently hatch, the treatment will be too weak to be effective against them and they will be free to begin a new outbreak.
Alternatively, if the second dose is delayed, there is the possibility that the new generation will have had time to hatch and to begin to produce eggs of their own. This new generation of adults will be killed by the second treatment but the eggs they have just laid will survive and will be able to begin a new outbreak when they hatch.
Different parasites have different life cycles and these life cycles are dependent on temperature. It is important, therefore, to carefully follow the manufacturer’s instructions, not only for the amount that is to be used, but also for the timing for subsequent doses in order to ensure that the treatment is as effective as possible.
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Should filters be turned off during treatments?
This is very controversial. Some people will advise you to shut off the filters in order not to harm your colonies of "friendly bugs” in the biological filter. The problem with this is that, if parasites or their eggs have been drawn into the filter system, they will not be killed by a treatment that is confined only to the pond. When the filters are turned back on, they will be washed into the pond to start a new outbreak.
I will risk sticking my head above the parapet and recommend that you leave the filters running so that any parasites in them are also killed. The “friendly bugs” (Nitrosomonas and Nitrobacter) in the biological filter are tougher than we give them credit for. Many treatments will have some effect on them but they will soon recover. The reason that the “friendly bugs” are resistant to chemical attacks that will kill off free floating bacteria is that in the biological chamber, these colonies form into a “biofilm”. This means that the bacteria stick themselves together with strands called “Polysaccharide Links”. These can be thought of as microscopic sticky rubber bands. There are not only the bugs that we want, but also other bugs that have seized the opportunity to set up home on the biological media. When chemicals are put into the pond water, any free floating bacteria and those that are on the fish, are exposed to the full strength of the treatment. These will be killed.
In the biofilm, however, only the bacteria near the surface will get anywhere near the full dose. The bacteria deeper inside the biofilm will be protected by those nearer the surface and also by the strands making up the film itself. The surface bacteria may be killed, but in the very competitive world of bacteria, there will be many billions or trillions just below, that will seize the opportunity to multiply and take their place.
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Better safe than sorry
As a precaution, it is advisable to stop feeding whilst the treatment is active in the water. Some treatments, such as Potassium Permanganate, will have done their job and will begin losing strength within a few hours. Other treatments, such as Malachite Green, may last for a few days, only slowly deceasing in strength. The bacteria colony will not be functioning as normal during this time, and it may take a few days for it to fully recover. To ensure that it has fully recovered, it would be advisable to make sure that when you recommence feeding, you feed sparingly at first and carefully check the Ammonia and Nitrite levels. Testing twice a day is not too often until it is certain that these parameters are staying within acceptable limits. If the levels begin to rise, you should stop feeding and, if necessary, boost the filters to get them working at full efficiency again.
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Why is it necessary to increase aeration when treatments are added to a pond?
Koi need a dissolved Oxygen level of 7.0 to 8.0 p.p.m. to be active and healthy. OATA advise that 6.0 p.p.m. is the absolute minimum level. Koi will quickly die if the level should fall to 3.0 p.p.m. or lower. Many treatments, will dramatically reduce the level of dissolved Oxygen in the water, so unless you know for certain that this is not the case, it is safer to assume that they all do. For this reason it is essential that high aeration should be maintained during pond treatments. High aeration is especially necessary if a fish is taken out of the pond and given a short term bath using a higher concentration of medication as is sometimes recommended.
If the pond is well aerated, the dose has been accurately calculated and all other recommendations have been followed, there is very little chance that there will be a problem. However, it is good practice to keep an eye on the fish for a few hours after dosing a pond, or after adding a medication to a fish in a hospital tank, just in case they begin to show signs of distress. Chloramine T can be deactivated by dechlorinator. The strength of other treatments can be rapidly reduced by immediate large water changes. When topping up, use a hose pipe and dechlorinator instead of the slow trickle of a purifier, the aim is to reduce the concentration by diluting it. Draining water from the pond will not actually reduce the concentration of an overdose, it will only make space for fresh water. It is the fresh water that will dilute the treatment and so the quicker this is achieved, the better.
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