The British Koi-Keepers Society     


Diagnosing Problems

One of the most difficult situations a koi keeper will experience is when he or she is confronted with a sudden problem. 

The first thing we think about is, where do we go from here? In other words, where do we start to diagnose the problem. The problem may have been in stages of development over the previous days weeks or even months. The first thing is not to panic and reach for the first chemical that comes to hand, using remedies for parasites, bacteria or fungus. 

We then start to use the process of elimination. First we check all the water parameters that are possible, at the same time observing the condition of the fish i.e. are they flicking or flashing, are they looking for oxygen, are they laid on the bottom motionless with clamped fins, are they hovering mid water with an increased respiration rate, have they gone off their food, are there any open wounds visible or any other symptoms you may think abnormal or relevant ? Any one of the above symptoms can send you flying off in a different direction. This is why authors find it difficult to put diagnostic measures into writing and prefer to put it into chart form. Sometimes charts can be a little confusing, when two or more symptoms arise we then wonder which line of investigation to follow. They do not always tell you how to solve the problem either, they merely tell you what the cause could be.

Water parameters in the first place are usually the culprits, although at the time of checking it may have cleared itself due to various reasons, i.e. water changes. Even a change in water temperature can change water parameters, temperature and pH can change the toxicity of ammonia. Higher water temperatures carry less oxygen, this also applies at night to a heavily planted pond, or a pond with a high algae bloom. There is also oxygen depletion when chemicals are added, even adding salt, or when thundery weather is about, all these things reduce oxygen levels.

With all problems there is usually a development stage, the length of which will vary depending what the problem is. For instance, if you have an unfriendly neighbour who happens to throw a bottle of nasty substance into your pond, the development time will be immediate. If a natural water parameter fails, the development time could be weeks before you spot the symptoms that your fish convey, unless you check your water on a regular basis. If you spot areas of active bacterial ulceration with a fungus covering, the root of the problem most likely started weeks before, as they are usually secondary infections they will attack any area where the fishes defense system has been breached, either by physical damage or parasite infestation. 

Average problems usually start from two sources, first water quality and secondly parasite infestation. Water quality is the most important, anything can develop from poor water, the fish are stressed trying to deal with the adverse conditions, their immune and defense systems become less effective and parasites that are normally under control get the upper hand. Fish are also prone to attack from certain parasites, even if they are healthy and no other problem exists. These can be parasites that are introduced by adding new stock, or placed in the pond on plants etc., such as leech, anchor worm and fish louse.

So where do we go from here ?

First lets take water quality. Say we find a problem where we find an adverse test reading. Say we have a toxic situation like ammonia or nitrite (either of these conditions will convey similar symptoms to a parasite infestation), straight away we know we have a problem with the biological side of the filtration. If the problem suddenly arises where it has been all right in the past, we can assume something has changed along the way. This is where we must put our thinking caps on and ask ourselves if it is something we have changed in the recent past or could it be some natural change over a period. 

If it is something you have changed it could be that you have added more fish to your pond for instance, or due to excessive feeding. If it is due to a natural change it could be that your filter is blocked and has started to track. It could be you have used a stronger bactericide than normal, or it could be due to the presence of chlorine after a big water change if you have not used a water purifier, you could have excessive anaerobic conditions due to dead bacteria and filter bottom sediment, all the nasties that give you the rotten egg smell. A blocked filter will not create enough area where aerobic bacteria can thrive, therefore the nitrogen cycle will not take place properly, simply because it will be starved of oxygen due to less available surface area. So in the first instance it would mean regulating your stocking level, or cut out the excessive feeding, or increase the size of your filters. In the second instance it would mean carefully cleaning out your filters, one chamber at a time, giving time in between to give that chamber time to catch up. In the meantime water changes would be advisable through a water purifier. The same solution would apply for ammonia or nitrite.

If we find pH levels fluctuating, again we must think what circumstances could be causing the change. Is it internal or external? Again ask yourself if you have made any external changes to the pond or the pond surrounds. Is your pond raised above ground level, or is it below ground level ? If so could there be run off after rainfall making it’s way into the pond, or is the problem acid rain. Have you applied cement recently to the waterfall or the surrounding rockery ? Is there any peat based soil in the vicinity. Basically what we are looking for is anything with an acidic base if there is a pH drop, or anything with an alkaline base in the case of a pH rise. Remember, if there is regular pH fluctuation day to night it could be due to a heavy algae bloom or to excess plant life. Just to recap, preliminary tests should include ammonia, nitrite, pH and temperature. Other water tests should include oxygen, nitrate, hardness, alkalinity, copper, salinity and chlorine. All are relevant and can affect water chemistry. Even if we are happy with our tests so far, it still does not eliminate water quality completely, which we will deal with later.

Now let’s take a look at internal reasons for pH fluctuations. We have already mentioned algae bloom and excessive plant life, stocking levels can also have a profound effect on the pH value. Carbon dioxide given off by fishes gills readily associates with water to form carbonic acid, encouraging a pH drop. A pond with heavy algae or excessive plant life will take up carbon dioxide and release oxygen during the daylight hours hence the rise in pH during the day. During the hours of darkness the pond will take up oxygen, and release carbon dioxide thus giving you a drop in pH during the night. Large volume air input will also drive off unwanted carbon dioxide, again encouraging a rise in pH. Biological filtration has a very decisive effect on pH. It consists essentially of two processes, both carried out by colonies of bacteria in the filter media. Nitrification, in which toxic substances such as ammonia in fish waste are broken down into nitrites and then into less harmful nitrates, and denitrification which occurs in special filters, where nitrates are converted eventually into free nitrogen gas and oxygen. These processes exert opposing effects on the pH value of water. The hydrogen and nitrate ions released during nitrification in effect produce nitric acid and thus lower the pH value. Denitrification by removing the acidifying nitrate ions causes the pH value to rise. To fully understand this process one would have to brush up on their knowledge of water chemistry. Basically the answer to this problem is keep your filters in good order and they should serve you well. Also keep an eye on stocking levels, any adverse conditions in water quality must be rectified first. We cannot expect fish to recover in poor water. Once we get the water right, then we can concentrate on the fish.

The next step would be to observe the visible symptoms. I have already mentioned quite a few symptoms easy to spot. The first thing we would take note of is, are all the fish affected or is it just one or two. If all the fish are affected we could expect either a parasite problem or a toxic condition. (Remember I said I would deal with further water problems later). Our next step would be to check for parasites. We would take one or two fish at random, take scrapes and see what the microscope revealed. Different parasites cause different symptoms. Some larger parasites such as Argulus, Lernea or Leech can be seen by the naked eye. In the early stages these parasites create no immediate reaction from the fish, it is only when they are present in large numbers does the fish show any reaction, and of course they are visible, giving you time to react before that stage is reached. We do find a different story with the smaller parasites like skin fluke, gill fluke, costia, trichodina and chilodonella. Fish suffering from any of these in excess would probably be off their food, lethargic and in some cases seeking out oxygen. We must of course mention the dreaded white spot. Fortunately it is easy to identify and responds well to proper treatment, but it must be dealt with promptly. It can also be seen with the naked eye. Any of the smaller parasites can be identified with an experienced eye through the microscope, and dealt with using the appropriate treatment. When we are dealing with larger parasites such as Argulus, Lernea and Leech it is always advisable to initially remove them manually with the fish under anaesthetic, then treat the pond generally. All the fish must have a thorough inspection, making sure to look on the underside. We would be looking for any breaks in the skin or any raised scales, excess mucus production, lumps or bumps or any reddened areas. Also check inside and outside the mouth area. Check gill filaments. These should be a nice deep red colour and should be evenly spaced like a comb. No white deposits in the form of excess mucus or gunge should be present, and no fusing of the filaments. Take particular notice of the finage as these areas tend to be the first to suffer from poor water quality. Also check the vent area for any inflammation or irregular discharge which may indicate some internal problem, in which case you may need professional help and advice. If during our inspection we find raised scales, it is usually associated with inflammation of some kind, eventually lifting the scales off. We may find wounds or ulcerated areas, which would need topical treatment in the first instant. To carry out proper treatment the fish must be placed under anaesthetic.

In the case of raised scales, using a pair of tweezers and giving the suspect scale a slight tug will reveal whether or not the scale root is damaged. If it is, it will easily lift off. For topical treatments to be at all effective the initial cleaning of the area must be thorough. Damaged scales should be removed so the affected areas can be reached properly with the medication. There are various medications on the market which one can obtain to carry out topical treatments. Specialist dealers such as Lincolnshire Fish Health sell their own branded products, some of which are in handy aerosol form. Just one word of advice if you are using aerosols, mask the area you are treating to avoid overspray on to other parts of the body, special care must be taken to protect the gills, eyes, nostrils and mouth. If you cannot obtain such products others are more readily available from your local chemist. For instance, T.C.P. and Friars Balsam. A bactericide called Myxazin can be obtained from any aquatic outlet or tropical fish dealer. Myxazin comes in handy small bottles with a stopper in the top which is ideal for transferring the chemical on to a cotton wool bud. The procedure would be to thoroughly clean the affected area first with T.C.P. then dab with a cotton wool ball or tissue until it is reasonably dry. Next apply the Myxazin with a cotton wool bud, again dab excess dry and finally apply Friars Balsam with a cotton wool ball. Allow drying time before returning the fish to water. A word of advice, do not apply Friars Balsam with a brush because after the initial application, the brush will harden and be of no further use. After the initial application T.C.P. should not be needed, Myxazin and a sealer should be sufficient. After two or three applications you should see some progress. The affected area will appear to be a lot cleaner and less active. It should be taking on more of a white appearance, rather than the mixture of red, orange or yellow. If that sequence does not appear then stronger measures may be needed. If only one or two fish are showing adverse signs, carry out the same procedure as already explained, as others could be in the development stage. The only exception would be in the case of individual physical damage.

So where do we go from here?

By stronger measures I refer to antibiotics. If that is the case the procedure would be as follows. Contact the B.K.K.S. Koi Health Forum, (provided you are a Society member) locate your nearest Forum member and ask for his or her assistance. A sterile swab would be taken from the affected area and sent to a laboratory for analysis, which would be in the form of a antibiogram. This would reveal which strain or strains of bacteria are causing the problem, or any other problem that may arise. You would receive a copy of the antibiogram showing a recommendation as to which antibiotic would be most appropriate. This could then be passed on to your vet who would supply the necessary antibiotic. The Forum member would then assist you to administer the treatment if required. At this stage I must add that the swab should be taken by an experienced person. If it is not done properly the swab can be deemed useless and a further one would have to be taken. This would be valuable time wasted both from the fish point of view and the laboratory. Also at your request the Forum member would keep an eye on your koi’s progress throughout the treatment period. There are obvious advantages for the Forum member to pay you a visit. Whilst they are there, they may spot potential problem areas in your pond or filter design, again you would benefit from this experience free of charge. The only charge they would expect is a mileage allowance, and possibly a nominal charge for any of their own medications they may use. Now you may remember I said I would deal with further water quality at a later stage. Let us assume you have carried out as many water tests as you possibly can, and they are all test perfect. You then naturally assume your water is not the problem. You carry on to treat your fish accordingly, but after a period you seem to have a persistent problem with your fish. It may be the case that your water is still at fault. You may still have a toxic situation that your previous tests have not brought to light. The fortunate part is, these cases are rare, but on occasions it does arise.

So where do we go from here?

It will mean a deeper analysis of your water. Their are various people who will do this for you. The Environment Agency for instance, will accept a sample of your pond water and supply you with an in depth report. There may be excess quantities of heavy metals in your mains water supply. These would be a problem especially if you were not using a water purifier for water changes or top ups. There may be a steady build up of theses metal particles due to your pond system. One typical example would be a copper build up due to a low pH, having a gas boiler in circuit with a copper heat exchanger, or copper from certain types of circulation pumps. An acidic pH puts copper into solution. There may be other sources of toxic substances, depending on your own particular circumstances. Your pond may be fibreglassed and there may be leaching from such a process. I am afraid it is any port in a storm. At this stage we are searching for the unusual. Some such instances could be weed killers on lawns, overspray from a farmer spraying his fields, poisonous plants or shrubs recently planted and so the possibilities go on. The staining of woodwork on pond surrounds, fencing, pergolas, roofing and side walls in indoor systems, air pumps picking up toxic fumes in indoor systems from paraffin heaters or paint brush cleaners, and the list goes on. At this stage we are clutching at straws and anything is a possibility. You may have noticed there has been no mention of viral infections, the reason being that viral infections are very rare and few treatments are available. Professional help would be required to diagnose in any case. We are all aware of the most common one, carp pox, and we have to depend on the fishes own immune system to cope with it. Sometimes the fish will beat it as it grows older, also higher temperatures will help.