T: Pond Keeping Terms – Tapeworm to Treatment


Tapeworms are one of the largest parasites to affect koi. Living in the intestine or body cavity, these mouth-less parasites absorb nutrients directly through their skin from the koi.

They are considered to be rare in the hobby for several reasons.

1. They are difficult to diagnose as their location means that unlike other koi parasites they cannot be viewed with the naked eye. In addition, even if they are present in a koi, they are only likely to cause minor chronic conditions, going largely unnoticed. Extremely rare cases see fish swell up around the ‘belly’ area, impairing the swimming activity.

2. They have a complex life cycle involving 2 other hosts besides koi. As koi are routinely held within relatively hygienic, predator-protected ponds, the likelihood of the parasite’s life cycle being completed is remote. Predatory birds consume an infested fish and excrete tapeworm eggs which enter the water, hatching to find live food as an intermediate host. These could include daphnia or copepods, both of which rarely occur in highly filtered koi ponds. The koi then becomes infected by eating infected daphnia.

As most koi are farmed in semi-natural conditions where predatory birds and daphnia may both occur, it is not unlikely for koi to become parasitised by tapeworms, and is quite likely that a good number of koi that enter the market each year are carrying tapeworms. Fortunately, it is unlikely that once in a pond, they will cross contaminate other fish.

Drugs can be administered against tapeworms, but are rarely considered necessary.


Many as aspects of a koi’s lifestyle are controlled by water temperature. The natural extremities of temperature determine which geographical areas will support koi, and with koi being able to tolerate a huge range of water temperatures, their global distribution is very impressive. Naturally a warm water fish, studies have shown that koi grow optimally at 270C, benefiting from temperatures that are stable and not prone to rise or fall.

Water temperature determines when koi begin to be active and use energy, leading to an increase in their appetite. As the temperature rises, a koi’s ability at converting that food into growth also improves, and is why koi should be offered a higher protein ‘growth’ diet in warmer temperatures.

As koi are poikilothermic they are slaves to temperature, having no choice but to respond to their environment. Breeding is a good example. Koi will always spawn in the warmer months, and only then when they have experienced a peak in water temperature of around 20-220C. The probability of koi spawning at cooler temperatures is greatly reduced, as specific hormonal interactions rely on environmental cues including temperature to stimulate spawning behaviour.

Because koi body temperatures are determined by water temperature, koi are particularly prone to stress where they are moved between water of widely differing temperature. Their physiology is unable to cope with such rapid and extreme changes (as they are out of their natural limits) and respond unfavourably to such conditions; hence the need for acclimatising koi and floating bags prior to releasing newly purchased koi.

Water temperature, besides having a massive controlling factor on koi, also has profound effects on the living pond and filter system.

Bio-filters are relatively inactive below 100C (and it’s a good job koi are too!) and will multiply when temperatures improve. Likewise the dissolved oxygen levels within ponds will also fluctuate with temperature, being lowest at high temperatures and vice versa, contrary to the requirements of all aquatic oxygen consumers. This is why ponds should be actively aerated through warmer weather.

Test Kits

It’s a shame we can’t determine the suitability of water just by looking at it or smelling it. There are so many different characteristics that water can adopt that don’t change its appearance, but can nevertheless have a significant effect on the health of koi. Water is the world’s best solvent, in that more compounds will dissolve in it compared to anything else. Many substances that may occur in even the slightest concentration, can have a major impact on fish, even though, the water may appear (and taste) fine to us. Hence the need for test kits.

Test kits have been instrumental in opening the fish keeping world to the issue of water quality – one that is fundamental to the success in the hobby. Test kits have not simply been a source of valuable information on the qualities of water, they have also improved the understanding of water quality and enabled us to take our koi keeping standards to a higher level.

The range of test kits available matches the number of criteria that are acknowledged as important to the health of a pond. The chemistry of the water can be analysed by testing pH, KH and GH while biological characteristics such as ammonia, nitrite and nitrate can also be tested to determine any direct impact a fish population may be having on their environment.

More recently, phosphate has risen as a worthwhile test due to its influence on algae in the pond. There is a great temptation to believe that the handful of tests will give the definitive analysis of pond water. However, there are many other influential factors that are easily overlooked or assumed to be of no consequence to the fish.

Test kits come in a number of different forms depending on the reagents used. All are colourmetric in that they produce a coloured reaction in response to the level detected by the test. The most popular form of test kit is the liquid reagent kit, where drops of reagent are dropped into a test vial. An alternative is the dry tablet test kit which is also dropped into a test vial. A more innovative kit uses dip-strips which are strips of paper that are impregnated with dry reagent. The strip is dipped into the water for 2-3 seconds and left for the strip to change colour. Some test strips now test for several different parameters on one strip.

Test kits should be purchased and used well before any fish are introduced to a new pond and should be used regularly as the pond and filter matures, ensuring that fish are stocked safely and that a stable pH is maintained.

Having gathered your pond’s water quality data, it must be interpreted and acted upon if required. Otherwise, there is little or no benefit to be gained from testing the water in the first place.


Koi are very well travelled fish. When considering the distance koi have travelled to get to our pond, providing them with the best conditions at their final destination is all they deserve.

Koi breeders and exporters have had many years’ experience of packaging and transporting koi thousands of miles, and we can learn from their experiences to enable koi to make their final ‘hop’ from retailer to pond as stress-free and low risk as possible.

Three aspects to keep a check on when transporting koi are:-

Dissolved Oxygen, temperature and water quality. Any competent koi dealer should bag and box your fish professionally, following commonsense guidelines.

1. Oxygen. Koi will be bagged or double-bagged in clear polythene bags which will contain sufficient water to cover the fish with the majority of the bag’s volume being taken up with oxygen. Most dealers will inflate the bag with pure oxygen from a cylinder but for shorter journeys air will suffice.

2. Water quality. Too many koi in a bag will cause water quality to deteriorate rapidly. Ensure that a bag is under stocked with koi, especially if a long journey lies ahead. Upon arrival, float the bag on the pond or quarantine system for 5 minutes and with the neck of the bag rolled down, introduce some of your system water to help mix the temperature and water quality, reducing stress upon introduction.

3. Temperature. During transit, such a small body of water can suffer extreme fluctuations in temperature. Stored in the shade of a vehicle and in a box (which will also reduce stress of bright sunlight) the temperature should remain acceptable, making it an easy task to equalise water temperatures during floating. Some ornamental fish exporters pack the fish boxes with ice packs to keep temperature under control and reduce the rate at which fish might pollute their water. This means that water quality in transit remains acceptable for longer.


The process of administering an appropriate medication (see AUG 2000 A-Z) in a manner that is suitable for the affected fish, unaffected fish and pond environment. A swift and accurate diagnosis is required to select the most effective medication which must then be administered in the correct close and over the correct period to be effective.


Trichodina is a microscopic external parasite that lives on the skin and mucus of koi and other fish. It is only visible under a microscope, and is easily identifiable as probably one of the most distinct koi parasites, spinning UFO style as a flying saucer. As it can’t be seen with the naked eye, Trichodina and other similar external parasites give themselves away by causing affected koi to secrete excessive amounts of mucus in response.

Consequently, the colours of fish take on a milky-hue and koi behaviour will probably become quite sluggish with a tendency to hang listlessly around the pond edges. This ectoparasite can be treated very effectively using anti-parasitic pond treatments that are available from aquatic retailers, being sure to complete the treatment to catch all stages of this pest.all stages of this pest.

Kill blanketweed and string algae.