Below FAQs are some common concerns of our clients before purchasing the Koi Carp if you have other questions, please just send it to
The diet of a Koi Carp changes with the seasons. In late spring and summer months when the temperature exceeds 16°C, the fish’s digestive system becomes fully active and fish will display voracious behaviour and should be fed a high protein koi stick.  In early spring and autumn typically, when the temperature is between 8-16°C, it is recommended to feed your fish an easy to digest food source such as wheat germ. Wheat germ is high in complex carbohydrates which releases energy much more slowly and is better suited to the fishes slowing metabolism.  During winter months or when the temperatures is below 10°C, the fish’s digestive system effectively shuts down. Therefore, when this happens, it is recommended to stop feeding your koi. If Koi sticks are left uneaten, it can negatively affect the water quality, so learn to recognise and understand your Koi’s feeding behaviour.  Good quality koi feed should promote fish health, alongside growth and colour. It will often include vitamins, proteins and carbohydrates which are vital to the fishes development. 
The size of a Koi Carp largely depends on the parent stock. Typically, Koi will grow between 22” and 36”. Japanese stock generally tends to be larger, with examples of specimen fish measuring as much as 48” and weighing 90lb.  
The quantity of Koi suitable in a pond, largely depends on your filtration system. While some filters state processable feeding rates, it is best to keep an eye on your nitrite levels. Nitrite levels should not exceed 0.2mg/l. If rates are consistently higher than this fish must be removed from the pond, or a larger filtration system must be installed.  Overcrowding a pond causes higher nitrite levels, which in turn results in stressed fish with weakened immune systems. The end result to this unfortunately is fish fatalities. Please come and take advantage of free water testing if you’re at all unsure/concerned about this. 
Koi can live in the pond during freezing temperatures. If you begin to notice your pond icing over, carefully ensure there is a hole in the ice at all times to transfer oxygen/carbon dioxide.  Waterfalls and air stones often help however if this becomes ineffective, an acetate sheet laid over the pond will also work. Never strike the ice with a heavy object as this will scare the fish while they are hibernating.  Excessively low temperatures can cause irreparable damage to the fish’s swim bladder. If you experience regular extreme weather conditions, we would always recommend installing a heating solution (such as an air source heat pump) to the pond. 
Koi Carp (Cyprinus carpio) and Goldfish (Carssius auratus) are both fish belonging to the same family, Cyprinidae. The main difference between the two is in size, goldfish typically growing to 8” and Koi much larger. As a result, goldfish tend to be easier to keep as they eat less and produce less waste making them suitable for small garden ponds.  Goldfish much like Koi come in a variety of colours including red, orange, "gold", white, black, and yellow. Selective breeding over 1,000 years has led to various body shapes, fin types and eye configurations. While goldfish tend to be cheaper than Koi, specimens such as the red-Oranda can fetch as much as £4,500. 
Koi Carp have an omnivorous diet, meaning they will eat foods of both plant and animal origin. In the wild this would be a varied diet consisting of shrimp, worms, insects water plants and fruit to name a few. Due to their nature this means Koi will take an easy meal of Koi fry (tiny juvenile fish) or eggs, however small pond fish larger than 1” will be safe.
Much like our buying guide suggests, the health of the fish and thus the body conformation is most important (i.e. no physical defects). After this, colour, patterning and skin lustre should be taken into consideration. As most people won’t be entering their Koi to compete, remember beauty is in the eye of the beholder!
Usually, green tinged water is caused by free floating algae. This would suggest you require a UV lighting steriliser on the pond. It may be you already have one, and the tube has failed and needs replacing, or you need to install one for the first time. 
While ducks are nice to look at, certain species may eat smaller Koi, and can even introduce parasites to your pond. They will also inevitably foul up the pond with their waste which your filter may not be prepared for. Our advice is to discourage ducks if you see them taking to your pond.  If you keep domesticated pet ducks and would like them to swim in the pond, ensure your filtration system is up to the job of handling the additional waste matter. Monitor the nitrite levels and assess the situation accordingly. 
While aquatic plants such as water lilies look vibrant in ponds, please be aware Koi Carp love to eat pond plants. Smaller Koi Carp tend not to do much damage, however larger fish will often uproot your favourite water lilies. There are a number of ways around this, such as using cleverly designed pond shelving to deter fish, cordoning off an area of the pond, or having an adjacent or connected pond for planting. 
Your filtration system should be doing most of the work, combined with manually removing leaves and other debris from the pond surface using a fine mesh net. If however you’re plagued with silt, leaves, pebbles and sludge on the bottom of your pond, a pond vacuum may well be the answer. Pond vacuums make light work of any debris in the pond and often come with an extensive range of cleaning apparatus.  We would never recommend doing a complete water change as you will often lose vital nitrifying bacteria which are present in healthy ponds. We recommend doing a 10% water change monthly, followed by topping the pond up with an inline dechlorinating filter attached to a garden hose. 
This is most likely an ulcer. Koi carp are prone to getting ulcers from injury or parasites. Ulcers form when there is damage to the slime coat and inevitably scales of the fish allowing potentially harmful bacteria to enter the wound. Ulcers can be treated with various medications. We would recommend seeking consultation on best way of treating your Koi. 
At Complete Koi & Aquatics, we do not take any fish back once they have left our facility. We ONLY bring in Koi from trusted breeders. We have extremely strict quality and healthcare measures and bringing a fish into our facility from an unknown source would compromise these protocols. If your fish is sick, we do provide free fish scrapes, which we analyse by microscope to identify possible illnesses. 
Koi Carp actually originate from a single black Chinese Amur Carp which was brought into Japan during the Chinese invasions of 200BC. The species has always had naturally occurring skin colour mutations, however it was the Japanese that selectively bred these fish to standardise and enhance the colours present in Koi Carp today. Japanese rice farmers originally kept the fish as a source of food, however they began gaining great pleasure from the bright colours of Koi Carp, and breeding as we know it started followed in the 1800’s.
Much like anything, Koi carp come in varying shapes, sizes and levels of quality. Baring this in mind small, single fish start for as little as £3. Overtime this fish will grow and change significantly, so to be sure you’re getting the best end-result it is worth spending a little more on small fish. Look out for A grade or handpicked.
Although Koi Carp can be great value, there are exceptions to the rule. Prize winning competition fish such as ‘S Legend’ (an All Japan Koi Show prize winning Kohaku) can sell for as much as £1,400,000. The fish has a length of 101cm which is considered to be large, amongst having an almost perfect body shape and immaculate kohaku markings of deep red set against pure white. The fish has been purchased for breeding purposes and is set to produce over 500,000 eggs.
While the Japanese are considered to be the founding father and experts of Koi Carp, each breeder concentrating on a specific variety in order to achieve perfection, there are other countries producing top quality fish: Israel - Israel have taken the Japanese process to their communal Kibbutz and made it semi-intensive, creating the largest Koi production facilities in the world. Israel is now producing high-quality, healthy Koi Carp which have a world-wide market to suit.
Poland – Fairly new to the market, breeder Jos Aben of Yoshikigoi Farm is now considered to be one of the top breeders of Doitsu (scales along the lateral and/or dorsal line OR scaleless) Koi Carp.
UK – Yes the UK (surprisingly) produces Koi Carp at farms such as Cuttlebrook and Newforest. The UK have had varying levels of success in producing quality Koi Carp, however they have won awards and the fish are hardy to local weather conditions which comes with its perks.
To summarise, Koi Carp are bred worldwide to varying levels of success and quality.
Healthy Koi Carp in the UK will typically live 30+ years, so be prepared to commit to the fish.
While this a typical lifespan, they have been known to live much longer. Legendary Japanese fish, Hanako reported lived to the ripe old age of 226. In the unlikely circumstances you happen to purchase such a hardy fish, be prepared to pass the Koi down to your grandchildren!
This really is a myth. Koi Carp may start small, but they can get especially large so ensure you have the space for them. Koi carp will typically grow between 24 – 36 inches in length, however some fish may well exceed 52 inches. Typically these tend to be Ghost Koi and Chargoi which tend to feed more.
Koi Carp aren’t too fussy about the quality of water they live in. Koi like to root around in natural, murky, mud ponds and are often kept in such conditions by experienced breeders. The only creature likely to be bothered about the water clarity is you!
Typically, the fish can withstand temperatures between 4 - 32°C, and thrive between pH 7.0 – 8.6. Water hardness is a consideration for Koi keeping though. Soft water (i.e. water which contains low levels of ions such as Calcium and Magnesium) make osmoregulation difficult for freshwater fish such as Koi Carp, and this in effect leads to stress and a weakened immune system. Koi keepers in areas such as greater Manchester (which has prolifically soft water) can expect to maintain health pond chemistry with GH (General Hardness) and KH (Carbonate Hardness) buffers.
Free water analysis is available at Complete Koi and Aquatics.
Koi keepers often become completely besotted with their fish and will spend many hours working and maintaining their ponds to the highest of standards. The reality is, nature will often thrive by itself, and the Koi keepers enjoy working on their pond.
Koi Carp are part of the Cyprinus family, which is one of the most pervasive fish families in existence. Carp of different varieties can be found worldwide with the exception of the poles.
It is often said that fish have a 3 second memory. This isn’t true! Koi have individual personalities and can display mood changes linked to water quality. Koi will often come up to feed when they see their owner, and with some persistence and regular interaction they can be even trained to eat out of your hand.
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