Koi, Ponds & Gardens – The Koi FAQ

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Frequently Asked Questions (FAQ) List


EQUIPMENT                                                                     (back to top)

imageQ Should a waterfall be turned off in winter?
Most certainly, yes. In an unheated pond, fish will tend to huddle together at the bottom. A running waterfall will not only disturb their ‘enforced rest’ (and thereby wasting valuable energy) but will also have the effect of lowering pond temperatures even more.

Q During winter is it advisable to turn off pumps and filters?
No, never do this. By all means reduce the flow rate of the pump, if it is possible. Filters should only be non-operational for maintenance reasons and then this should only be for the shortest time possible.

Q What is a Hi-Blow?
It’s probably the most popular air pump in the UK. It’s used with airlines to power air stones in filter bays and, or ponds for excellent aeration.

Q Will an ultra-violet (UV) unit kill blanket weed?
No, sadly not. However, it will most certainly effectively eliminate green water.

Q What is the average effective life for a UV tube?
This depends upon whether or not it is switched off during the long winter months. Either way, to ensure constant performance, it should be changed annually – usually in the spring.

Q What is a Koi sock?
This is a fine mesh, soft net, about 36 in long and open ended. It is attached at one end to an 8in-11in diameter head with a short handle. Having netted a Koi from the pond into a floating bowl, the Koi sock is a good way to move the fish to a polythene bag, for example.

FILTRATION                                                                    (back to top)

Q Would hair rollers be just as good as Flocor in a biological filter?
Yes, and they are probably a lot cheaper to buy brand new.

Q When cleaning any filter media, such as foam cartridges or matting, which water should he used?
Only pond water, never tap water.

Q What does Zeolite do?
When placed in a filter, it will absorb ammonia from the water. However, it has a limited life and requires ‘recharging’ in salt at regular intervals (l lb of salt per gallon for 24 hours).

Q Now big should a filter be?
As a general guideline, between a third and a half of the pond surface area.

Q Within a filtration system, what does “tracking” mean?
A dysfunctional fitter which does not have the facility to flush to waste, in every chamber, allows a build up of sludge. Eventually, this will block all or part of the media and the water passing through will create its own route. The end result is ‘tracking’. Bad news for the Koi.

Q What is the ideal retention time in a biological filter?
it depends on the size of the pond, but in order for the aerobic bacteria to be effective, aim for around 20 minutes.

Q What is new pond syndrome?
An immature filter on a new pond is the cause of this. Bearing in mind that it takes time to develop a population of micro-organisms within a filter, ammonia and nitrite readings will fluctuate. To allow the filter to develop adequately, fish should be gradually introduced, one or two at a time over a few months. Also, avoid overfeeding which again puts too much of a strain on an immature filter.

Q In establishing a new biological filter, is there a safe way to boost its performance?
Products such as ABA, Polybac, Activex, Bio-Claire Advance, to name but a few, will certainly do the trick here. Always follow the manufacturer’s instructions to the letter. Ask for your local Koi dealer’s help when choosing the right one (see Koi, Ponds & Gardens’ classified section to find your local dealer).

Q Name some reliable filter media?
A Without proper filtration Koi will not survive for very long, unlike the much hardier goldfish. Popular filter media includes Flocor, Bacballs, foam, Canterbury Spar and matting.

GENERAL                                                                         (back to top)

Q What effect does temperature have on Kol colours?
Very warm weather causes pigments to contract, whereas in lower water temperatures they expand. This means that the Koi look their best in cooler months.

Q Spring is often said to be a dangerous time for Koi – why is this?
Koi can adapt to constant temperatures, but our spring weather can often mean sunny days, with frosty nights. This abrupt change in temperature can be harmful to the Koi.

Q What is the average life expectancy for Koi?
This very much depends on the skill of the Koi keeper, the pond environment, stocking rates and actual health of an individual fish. For various reasons, some will die not long after being introduced into a pond. Others will thrive and can survive for upwards of 30 to 50 years, all things being equal.

Q How can I tell if Koi are male or female?
It’s difficult with small Koi. With adult fish, females are usually a more full cigar-shape, compared to leaner males.

Q What is the weight of 1,000 litres (imperial = 220 gallons) of water?
One ton.

Q Which is the most famous place in Japan for Koi?
Niigata is recognised as the home of Koi, where many top breeders and fabulous fish can be found.

Q How much should a good quality Koi cost?
It’s impossible to give a definitive answer. Koi come in a host of varieties and sizes, which is reflected in the selling price a dealer charges. The best quality comes from Japan and they will command a higher price. This is not because of the long journey to the UK (although, of course, that is a factor), but quite simply because they are superior fish. It is probably best to decide beforehand how much you want to spend, then shop around until you find that special Koi which is within your budget.

Q Price aside, what are the key points to look for when buying Koi?
Koi should be alert, eager to feed and free of blemishes, sores or split fins. Be wary of a fish that seems to be ‘sulking’ on its own or with clamped fins, as this indicates health problems. Always ask to see the fish bowled up, for closer inspection. Try to build a relationship with your local specialist Koi outlet and once this has been established you can buy with more confidence.

Q What is biomass?
This is a living organism of micro-organisms which breaks down harmful waste and removes toxins. The biomass performs best in temperatures of 100’C to 40’C, requires plenty of oxygen and an adequate source of food. It is nature’s helping hand for the Koi keeper and must be maintained at a high level. Beware of the use of chemicals in the pond, as this will reduce the biomass population considerably.

Q What is blanketweed and what causes it?
A Blanketweed is a filamentous algae of which there are several species. It is caused by a number of factors, chiefly nitrates in the water and prolonged exposure to sunshine.

Q What does the term ‘finished Koi’ mean?
A Some Koi look wonderful at an early age, they have in fact reached their peak too soon and as they grow older they do not maintain this look. Other Koi are often passed over by the inexperienced, but grow on to become stunning fish. Once a Koi is ‘finished’ it will get no better, often the reverse is the case. The secret in buying Koi of 6″ to 8″ is the ability to recognise future possible development.

Q How many eggs can a female Koi lay after spawning?
A Anything from 100,000 to 750,000 depending upon the condition and size of the female.

Q How can overstocking a pond be avoided?
A By strongly resisting the temptation to buy ‘just one more fish!’ Follow a stocking ratio of 24 square inches of pond surface area for each 1 inch of fish, including the tail. Remember to allow for future growth of the fish.

Q Are Israeli Koi as good as Japanese?
A Israeli Koi producers have made much progress in a short time and are to be commended for this. However, in most cases they have some way to go to catch up on the ‘Masters of the Art’, which the Japanese undoubtedly are.

HEALTH AND NUTRITION                                                 (back to top)

Q Within a quarantine system, is it okay to keep a Koi on its own?
Koi prefer to have some company, so it is best to always keep a couple of inexpensive Koi or goldfish in the quarantine. area at all times. Apart from anything else, the presence of fish will keep the filter ‘ticking over’.

Q Having bought a new Koi, how long should it be allowed to remain in the bag, floating on the surface of the quarantine pond?
Thirty minutes is the normal time to allow the temperature in the bag to equalise with that of the water.

Q Should all new Koi be quarantined or can they go straight into the pond?
A Too big a subject to cover fully here, but in a word, yes, quarantine is a must. It will minimise the risk of introducing problems into the pond.

Q With consistent Koi fatalities in a pond who can provide help?
There are several’sources of help – vets, Koi clubs, Koi specialist outlets, independent Koi consultants and experienced Koi keepers.

Q Having been torpid during winter, at what temperature does the Koi’s immune system regain efficiency?
Normally at about 13’C or 140’C, or 55’F to 57’F if you prefer Fahrenheit.

Q When adding necessary medication to the pond, is it okay to leave the UV unit on?
Always switch off the UV before treating a pond, as the UV light will reduce the effectiveness of the medication. Leave it off for three to five days to ensure the medication has had sufficient time to work.

Q If pond medication is unavoidable, how can the biomass be brought back up to strength again?
The products mentioned above are not only beneficial for starting up a new pond, they can be used on an ongoing basis to constantly boost the biological process.

Q What is carp pox?
A A common herpes-type, low temperature ailment, this virus can in particular affect young Koi. It looks like blobs of white candle wax on the body and fins. Although unsightly it is rarely serious to the wellbeing of the infected fish. It would be refused entry, for health reasons, at a show, so never attempt to exhibit a fish in this condition.

Q Is there a treatment for carp pox?
A No. There is no known cure but as warmer weather arrives, with the resultant increase in pond temperatures, the tumours should gradually disappear. Over the years, as young Koi reach adulthood they will grow out of carp pox.

Q What are ulcers?
A A sore on any part of the Koi’s body, normally attended with a secretion of pus or discharge. Without prompt treatment, ulcers will kill Koi.

Q What causes ulcers?
A Stress, poor water quality and a high level of aeromonas, usually the hydrophila strain. The only certain way to identify the bacteria is to take a sterile swab and send it for laboratory culture.

Q What causes fish to jump in the pond?
A Could be they are jumping for joy! More realistically, they are indicating that they are unhappy with their environment. Poor water quality can irritate their skins, so check the water for ammonia and nitrite. The other alternative could be a sudden increase in parasites which are causing the Koi distress.

Q What treatment should be given to Koi ‘flicking’ and ‘flashing’ in the pond?
A Before undertaking any treatment, first of all the problem should be identified. When visiting a doctor, they make a diagnosis, then offer a remedy. If unsure they will carry out tests and often do nothing. The same applies to Koi. Find out what is the root cause of the problem first, then treat accordingly.

Q What does dropsy look like?
A Scales will stick out like a pine cone and eyes bulge from the head. There are various contributing factors for this condition which in most cases is lethal.

Q What should Koi be fed at lower temperatures?
A It is generally accepted that easily digested, wheatgerm sticks or pellets are best, if Koi are still active and looking for food. Below 8°C they usually aren’t interested.

Q What are the dangers of low oxygen levels during very hot weather?
A If the dissolved oxygen content in the pond is too low, fish can quickly die. The biggest Koi will be the first to succumb. This can be prevented by having a Venturi and/or waterfall. Extra aeration can be provided by using a pump and airstones. Remember always to test for dissolved oxygen levels during very hot spells.

Q What is most commonly used to anaesthetise Koi which require treatment?
A MS222 is probably the favourite of most Koi keepers. It is a white powder, available from vets and should be administered at a rate of 1gram to 1 gallon of pond water.

Q Where can antibiotics be obtained?
A Antibiotics can only be prescribed by a vet who will need to know what their end use will be for.

Q Name some of the contributing factors to stress in Koi.
A 1) poor water quality; 2) overstocking; 3) change in environment; 4) over frequent netting and handling.

Q Often, after an illness, a doctor will prescribe a tonic, to aid recovery. Is there such a product available for Koi?
A Yes, Koi Vital (from Tetra) is very beneficial. Only use when temperature is over 10°F (50°F).

Q How can one be sure that pelleted food is really fresh?
A All the major, reputable Koi food manufacturers date stamp their products. Always check this before making a purchase. Never use opened boxes of food which have been kept over the winter. Q What is the problem with a Koi which has bulging eyes? A It would appear to have exophthaimus, better known as ‘pop eye’.

Q What is the best way to identify parasite infestation on Koi?
A Carefully take mucus scrapes for examination under a microscope. If numerous parasites are evident, take the correct steps to eradicate them.

Q Is it wise to medicate the pond in early spring and autumn to prevent parasites developing?
A No! Parasites are present on all Koi and a healthy fish has an immune system to cope with this. Continual additions of chemicals can be counter productive, in that they will destroy the filter biomass. Medication should only be done if it is essential, not on an ad hoc basis. Would you take cough mixture today to prevent a cough you might get tomorrow?

Q What is a topical treatment?
A A treatment used for direct application on wounds, sores and infections on fish.

Q What is a Koi’s first line of defence against parasites and disease?
A The mucous coat.

Q Are there any occasional ‘treats’ that Koi can be fed?
A Sliced oranges (with beneficial vitamin C) are a favourite, along with melons and loose leafed lettuce. Also popular are prawns, shrimps and cockles. Brown bread (often with honey) is usually acceptable.

Q Koi have been known to bleed from the gills when netted. What is the cause of this?
A This is a common stress reaction in some Koi.

Q What is the biggest single cause of Koi deaths?
A Very probably, bad Koi keeping!

POND BUILDING                                                              (back to top)

Q What is the best size for a Koi pond?
A As big as your funds will allow! Try to have a surface area of at least 80sq ft (8′ x 10′) and a minimum depth of 5ft, although 6ft would be even better.

Q What are the options to waterproof a pond?
A Butyl liner – fibreglass – pond paint – G4 – rein fibre.

Q When building a pond, which is better a butyl liner or fibreglassing?
A Good quality butyl liners can last twenty years or more and are certainly fit for the purpose of water proofing the pond. However, although more expensive initially, a professionally fibreglassed finish is far superior and will last much longer.

Q Would a 2,000 gallon pond, 2′ 6″ deep, be suitable for small Koi?
A Yes,, but not for long! Remember, small Koi will soon become big Koi and they will require a depth of at least 5 feet.

Q What is the most reliable way to determine the gallonage of a pond?
A The only really accurate method is with a flow meter, which should be used when the pond is first being filled.

Q How does a flow meter work?
A It is attached to the hose used for filling water from the mains. Make a note of the numbers on the dial before starting. When finished, write down the numbers now. Subtract one from the other and the difference is the gallonage of the pond. Quite similar to a trip meter in a car.

Q What are ‘dead” areas in a pond?
This usually occurs in an unusual or irregular-shaped pond, where it becomes difficult to circulate water properly. It results in areas of stagnant or dead water.

Q When building a Kol pond are bottom drains really necessary?
Without any doubt they are a vital part of any set up. Without the means to easily flush harmful waste products from the pond, the build up of toxins will cause health problems. The only other alternative is, of course, the use of a purpose-made pond vac. This is time consuming, needs to be done frequently and can disturb the fish. Who wants to be doing this on a rainy night when with a bottom drain, all that needs to be done is to pull a valve or standpipe?!

Q With a pond catching full sunlight for most of the day, would the extra expense of building a pergola reduce blanketweed?
A By denying the ‘dreaded weed’ sunlight it will arrest its growth dramatically. Ensure the pergola’s top is fully shaded.

SHOWS AND SOCIETIES                                                  (back to top)

Q What does BKKS stand for?
A The British Koi Keepers Society. The national body responsible for most Koi shows and clubs in the UK.

Q What does JSC stand for?
A The BKKS Judges and Standards Committee (JSC) is the authority responsible for matters relating to BKKS shows. Only BKKS approved Judges may officiate at BKKS open shows.

Q What is an open show?
A BKKS open shows are open to anyone. Exhibitors need not be BKKS members.

Q What is a closed show?
A Only Koi owned by members of the BKKS Section staging the show can be exhibited.

Q What is a BKKS section?
A Any group of full members of the Society who desire to work together in an area to further the objectives of the Society may collectively become a Section of the Society, subject to the approval of the National Council. Each Section shall consist of not less than ten full or trade members.

Q Is the JSC responsible for water quality at shows?
A No, it is the sole responsibility of the Show Committee to maintain acceptable water quality in the show vats for the full duration of the event. In order to assist Show Committees, the JSC recommend certain parameters in order to define acceptable water quality. Were these guidelines not being followed by a Show Committee the JSC would certainly want a full explanation.

Q What does benching mean?
A Benching is the inspection, measuring and classification of every Koi without which a show cannot proceed.

Q What is an English style show?
A A show where vats are allocated by owner so that a mixture of varieties and sizes of Koi are all together.

Q What is a Japanese style show?
A A show where the Koi are exhibited in vats according to size and variety irrespective of the owner.

Q What are the recognised show sizes for Koi?
A Size One: 1″ to 8″ Size Two: 8″ to 12″ Size Three: 12″ to 16″ Size Four: 16″ to 20″ Size Five: 20″ to 24″ Size Six: 24″ and over

Q How many Champions will be selected at an open show?
A Four. Grand Champion (Best Fish in Show) which is usually a Size 6 Koi; Mature Champion which is usually Size 5 or 6; Adult Champion which is usually Size 3 or 4; Baby Champion which is usually Size 1 or 2.

Q Which award is greater, Best in Variety or Best in Size?
A Best in Size. During the first round of competition the Judges pick a first, second and third in each variety and size. In round two the Koi that won first and second in variety are judged for Best in Size, in each of the six sizes.

Q Will show organisers allow inexpensive fish to be exhibited or are these events only for the ‘big spenders’?
A The only reason a fish would be refused entry into a show would be on health grounds. The quality or cost of a fish is of no concern to the organisers. Although naturally when judging takes place, the higher grade Koi will feature more prominently on the awards list.

VARIETIES                                                                       (back to top)

Q What does Nishikigoi mean?
It is the Japanese word for brocaded carp.

Q What does Go-Sanke mean?
A term used to collectively describe the ‘Big Three’ Koi classes – Kohaku, Sanke and Showa. Because they have a reasonable defined criteria they are harder to produce to a consistent standard. Therefore, they are more highly prized than other varieties.

Q Explain Kin Gin Rin.
A Kin Rin = highly reflective gold scales. Gin Rin = highly reflective silver scales. If the gold or silver scales are easily countable, then the fish is not Kin Gin Rin.

Q How many classes of metallic Koi are there?
A Three. Hikari Utsuri, Hikari Muji, Hikari Moyo.

Q How many classes of non-metallic Koi are there?
A Ten. Kohaku, Sanke, Showa, Utsuri Mono, Kin Gin Rin, Tancho, Asagi/Shusui, Bekko, Koromo and Kawarimono.

Q What is the most highly regarded Koi variety?
A Without doubt, the red and white Kohaku.

Q Of all the varieties of Koi, which is the easiest to hand feed?
A The Chagoi can be quickly tamed and soon allow the owner to hand feed it. Because of their serene nature they can have a calming influence on other fish also. But beware, Chagoi can grow quickly and will need a pond befitting their size.

Q Is there an easy way to tell the difference between a Shiro Utsuri and a Shiro Bekko?
A Both of course are black/white and can be confusing for a beginner. The Bekko has no black head markings.

Q Is there a difference between the Sumi (black) of a Showa and Sanke?
A Yes, the Sumi on a Sanke is smaller, usually above the lateral line and none on the head. With Showa the Sumi is large, often extending down over the abdomen.

Q What is the term used to describe a dapple pattern Koi?
A Kanoko.

WATER QUALITY                                                              (back to top)

Q What are the benefits of water purifiers?
They improve the water quality for Koi by treating chlorine, chloramine, pesticides, insecticides and ‘metals’ often present in mains water.

Q What is pH?
A On a scale of 1-14 it is a measurement of how acidic water is. Neutral = 7. Above 7 = alkaline water.

Q Of the various test kits on the market which are the most essential?
A Ammonia, nitrite and pH should be regularly checked and a log kept of the results. To get a true comparison, always test at the same hour. While not essential, it is nevertheless helpful to test for oxygen and nitrate levels also.

Q What is Montmorillonite clay?
A It gets its name from a French town where it was first mined in 1874. It has been used by the Japanese, in the form of the well known Refresh product, for many years.

Q What are the benefits of Montmorillonite clay?
A It promotes skin lustre, health and good water quality. It is well worth the outlay for the genuine product, which uses high quality clay with the correct mineral content.

Q With a newly built pond, how can one be sure that the water conditions are right for Koi?
A Once the system has been operating smoothly and all the test results appear satisfactory, introduce a couple of expendable fish first. If they survive for a week or two then it should be safe to slowly add the better Koi. Continue to monitor water parameters.

Q What is the ideal level of dissolved oxygen in a pond?
A A minimum of 6mg per litre, 8mg is better, while below 3mg per litre is lethal.

Q Water authorities add chlorine to tap water to make it safe for human consumption, but what danger does this present for Koi?
A Total chlorine, including free chlorine and chloramine, has the effect of burning fish gills. This prevents the absorption of the all important oxygen. To avoid this, always use a water purifier.

Q How often and how much water should be changed in a pond?
A Approximately 10% per week in the winter and 20% per week in the summer, although generally not all at once. Normally a flush to waste morning and evening in the high summer, particularly after feeding.

Q If a test shows a high ammonia reading in a new pond what action should be taken?
A Stop feeding at once. Carry out a 50% water change in the pond, using purified water if possible. Continue to change water daily until the levels of ammonia are down to nil.

…more to follow.

More FAQs will be added to the site in the coming months.
Please come back soon.

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