There is no substitute for a well-balanced dry food (good quality pellets) for koi collections. Modern koi foods are designed to give full nutritional value to koi, in other words a balanced diet. However, some koi keepers will mix two or more brands to compensate for the possible deficiencies that may exist in their favourite brand of koi food. Other koi keepers like to give koi special treats that the koi like during those precious relaxing times spend next to a pond. These treats may vary from brown bread with honey, lettuce, watermelon, oranges, cooked vegetables, lemons etc. Others will try more unusual treats like pink prawns, raw meat, silkworm pupae, earthworms, mealworms, bloodworms, mosquito larvae, and even tadpoles. Some of the above “live food” can be cultured at home while others are commercially available either in frozen or freeze-dried form at considerable expense.
It is essential that koi keepers understand the nutritional requirement of koi, and therefore it is suggested you read this article by Chris Neaves first.
Most animals in captivity relish live food as a supplement and Koi are no exception. One of the best and easiest ways to offer a healthy food to your koi is to offer natural, live worms or insects.
As a keeper of exotic finches it is almost a “must” for me to offer the finches some kind of live food in order for them to successfully raise their young. The choice is actually simple. You can either spend your weekends digging for termites or you can start keeping mealworms. Mealworms, Tenebrio molitor, are in a strict sense, insects. It is the larvae of the darkling beetle. The finches prefer mealworms that are relatively small, so it was inevitable that once the mealworm colony was up and running, one will sit with surplus fully grown mealworms that are unsuitable for finches, unless you are willing to chop them into small pieces or to scald then with boiling water. The next logical step was to feed the mealworms to the koi!
I have been feeding the surplus mealworms to my koi collection for considerable time. When I realized that the supply will not run out, I started to do some research about the nutritional value of these insects, because I needed to know if the mealworms were actually good for the fish. It must be pointed out again, that the mealworms described here, are the species, Tenebrio molitor, and not the “superworms” that is normally fed to reptiles. Superworms are nasty creatures, difficult to breed and there are reported cases where they have eaten their way out of a plastic container!
Research into mealworms inevitably led to researching other “live foods”, such as Silkworm pupae, Mosquito larvae, Bloodworms, Earthworms and Tadpoles. The biggest challenge that I faced was to determine the actual nutritional value of these critters. Some sources for instance, will indicate the crude protein value of the insect, while another source will indicate the crude protein value of the dried insect. Another challenge was the origin of the critters as well as the food that they were supplied with. It can therefore be assumed that other sources may differ from the values quoted in this article, but the differences will not be significant.
Basic Nutritional Value - Mealworms (live)
Crude Protein 20.27%
Crude Fat 12.72%
Crude Fiber 1.73%
Nutritional Value - Mealworms (Dried)
Crude Protein 60%
Crude Fat 24%
Crude Fiber 4.5%
Mealworms are a fantastic way of providing both nutritional and dietetic diversity. The nutritional values of these larvae are almost identical to the value of silkworm pupae and in some instances better. If one also considers the fact that one can “gut load” them with extra protein and vitamins, these insects can be a very valuable supplement to the normal dry feed.
The "common mealworm" (Tenebrio molitor) is probably the most widely raised feeder insect available. Mealworms are extremely easy to keep. If you have a surplus, just store them in your refrigerator where they go into a dormant state and last for months. Remove the mealworms from the refrigerator once per week, feed them for 24 hours, and then place them back into the refrigerator for long-term storage. Those mealworms that you intend to feed to the koi can be removed from the refrigerator and fed directly to the fish. If you want to go that extra mile, take them out 24 hours in advance and feed then a slice of potato sprinkled with calcium and vitamin powders. Experiments have shown that Oscars fed on mealworms grow at a considerable faster rate than those fed only on commercial foods.
When you first toss a mealworm into your pond most fish will ignore it. Mealworms are covered by a fairly tough shell that renders them tasteless or unappealing to fish encountering them for the first time. Break them in half the first few times you feed them. Fish can’t resist them once they try them. Few people will feed these mealworms to their young fry, but mealworms make a great food for larger fishes – about 10 cm or longer. You needn’t feed mass quantities of mealworms to your fish to get good results. Feed balanced dry food first, and then feed them the mealworms for dessert.
Mealworms are extremely easy to keep. There are literally thousands of web sites that explain how to keep mealworms and it is therefore not worthwhile to describe the whole process here. In short, if you are lucky enough to get hold of the beetles, you put them into a plastic crate with bedding. The cheapest and most suitable bedding is Digestive Bran that can be obtained from any Supermarket. Cut a Gem Squash in half and place it upside down on the bedding. Drill a few holes in the lid of the crate for ventilation and replace the lid. They will start laying eggs in no time! Most pet stores keep mealworms and one can purchase say 100 worms and start the process. Place them in Digestive Bran and provide half a gem squash. They will mature rapidly and turn into pupae. Depending upon temperature, it usually takes two weeks for the beetles to appear and to start propagating.
The newly hatched worms are very small but if one replaces the gem squash on a weekly basis, they will soon be visible and within a few weeks the freshest food supplement will be available for the fish to enjoy!
As explained earlier, the larvae go into “hibernation” when cold. They’ll keep this way for several weeks, maybe months. In the fridge they eventually dry up and/or get skinny. You can plump them up by warming them to room temperature and giving them a slice of potato for food and water. You can juice up your worms by sprinkling their potato slices with powdered calcium and vitamins.
If you’ve ever kept mealworms, you would have noticed that their faeces are dry as dust. They extract all moisture from their powdery droppings and can live on next to no water. The small pumpkin or a carrot that is placed on the bedding is the only source of moisture that they require. The fact that mealworms are kept in dry bedding eliminates the risk of transmitting any waterborne disease or parasite.
Consider the above and the availability as well as the expense of the various live foods and the feeding of mealworms makes more and more sense.
Cultures are easy to obtain.
Once several colonies are established, they will provide an endless supply of fresh live food.
Dietary value equals that of silkworm pupae.
Worms can be “gut-loaded” with extra nutrients.
With a little care, worms can be stored almost indefinitely in the refrigerator.
Mealworms live in a very dry environment and unlike mosquito larvae, bloodworms or tubifex worms, it poses little risk of disease transmission.
Mealworms have an exoskeleton made of chitin that is not easily digestible. Although I have not experienced this, it is possible that large quantities of mealworms may cause constipation in a fish.
Nutritional Value of Live Silkworm Pupae
Total Protein: 12 to 16 %
Total Fat: 11 to 20 %
Carbohydrate: 1.2 to 1.8 %
Ash 0.8 to 1.4 %
Nutritional Value of Silkworm Pupae meal (Dried)
Recently there has been a fairly intense hype about silkworm pupae in South Africa and it is even punted as the “secret” to successful koi keeping in Japan. The Japanese breeders use silkworm pupae extensively during the summer as part of the feeding regime to grow and prepare their koi for the market. Japanese hobbyists also use silkworm pupae to provide growth and improve body shape, colour and gloss in preparing their koi for shows.
Silkworm Pupae are the traditional food used many years ago as a staple diet for koi in Japan. The pupae were mixed with boiled rice (30:70) ratio. Even today the utilization of these “iconic” pupae is looked upon as the miracle food for koi and is the claim to fame of many koi food brands. The price of koi food containing silkworm pupae is staggering. The situation in India places a big question mark on these high prices, because numerous investigations have been launched there to determine an economic use for the excess pupae that is a by-product of the silk industry. These investigations were launched to counter the negative environmental impact caused by the decomposing pupae when thousands of tons are dumped annually.
Silkworm pupae are a recognised, iconic food supplement that has been used for centuries. Feed these pupae only as an occasional treat, or a maximum of 30%, of the daily feed
Silkworm pupae are high in fat
Excellent source of protein.
The neutral lipid of de-silked silkworm pupae was considered to be a good source of linolenic acid.
Rich in vitamin B
Should be fed sparingly
Very expensive and not easy to obtain.
Difficult to preserve
Pupa powder or dregs has low content of calcium and phosphorus.
There are unconfirmed reports that they may cause a diabetes-like disease in koi.
Nutritional Value of Mosquito larvae
Crude Protein 5.40%
Crude Fat 1.10%
Crude Fibre 1.00%
These larvae are mentioned here, mainly for the role that it play in the rearing of fry in mud ponds. Mosquito larvae are very small and do not play a major role as a food supplement in a normal koi pond, although the occasional mosquito larvae may find its way into it.
Mosquito larvae can be found in any stagnant pool of water and are therefore not difficult to cultivate. The main problem is to find a way of harvesting mosquito larvae during the short time that they are ready to be used as a food supplement and the moment that they become adult mosquitoes! These larvae are relatively small and are more suitable for fry and tropical fish. In most provinces of South Africa, mosquito larvae are a seasonal food because they can rarely be found in winter. As with many aquatic creatures, larvae are part of the natural food of small fish, but the transfer of waterborne parasites and disease remains a problem when harvesting mosquito larvae from natural sources. Cultivating mosquito larvae at home may result in strained family relations.
Can be found in any stagnant pool of water.
Young fish will appreciate these snacks
Mainly for small fish
Not very high in nutritional value
Possible transfer of parasites, predatory insects and disease.
Nutritional Value of Bloodworms
Crude Protein 8.3%
Crude Fat 1.2%
Crude Fibre 3.9%
(Protein as a percentage of dried bloodworms - 45.3%)
Bloodworms are larvae of the midge family Chironomidae. Not all chironomid larvae are red in colour. While the most common ones are red, they can also be green, brown, or black. Also some are transparent and are commonly known as Glass worms. However, only those that contain haemoglobin are red and hence the name “bloodworm”. They are therefore a good source of iron for the fish since they contain haemoglobin
Chironomidae larvae and pupae are highly nutritious and nourishing and constitute one of the staple food items of many fishes in their natural environment. They are a commonly used live or frozen food source for aquarium fish culture. Almost all fishes will greedily devour them when they are offered. Research has found that most fishes when provided with bloodworms as a supplementary food item have better growth and spawning rates.
Bloodworms as a fish food supplement are one of those topics that are the most hotly debated on every fish forum. The debates normally centres around the fact that it an aquatic insect and therefore poses a high risk of disease transmission. Secondly it is relative small and is only suitable for fry and maybe Tosai. Thirdly, it is a dirty smelly process to culture and it is a real mission to separate the worms from the decaying plant matter.
The solution is to buy bloodworms as either frozen cubes or in freeze-dried packages. Most uses for bloodworms relate to tropical fish. The main problem experienced with frozen bloodworms is the fact that they start decaying almost during the process of thawing. Freeze-dried bloodworms are reported to contain less nutritional value than live/frozen specimens.
Constitute one of the staple food items of many fishes in their natural environment.
Good source of iron for the fish since they contain haemoglobin.
Available over the counter in freeze dried or frozen form.
Can be cultivated at home.
Water smells very bad during cultivation of bloodworms.
Extremely difficult to harvest worms from between decaying plant matter.
Worms start decaying during thawing process.
High risk of disease transmission.
Suitable supplement mainly for small fish
Nutritional Value of Earthworms
Crude Protein: 10 to 20%
Crude fat (min): 2.5%
Crude Fibre (max): 0.2 %
Ash: 2,55 %
75 to 90% moisture in bodyweight
Nutritional Value of Earthworm meal (Dried)
Crude protein (min): 62%
Three are over 2200 species of earthworms known worldwide, each with its own unique nutrient composition. It was therefore decided to concentrate on the species E. Foetid. Earthworms can be fed to the fish all year round. If you can't or won’t dig them out of your garden, bait shops will be happy to sell you some. Earthworms are high in protein and when offered to koi, will soon become a favourite treat. It is a sure way to gain the affection of your koi. Earthworms ingest substrate directly. This makes them a very valuable source of minerals and trace elements, but it also raises the possibility of heavy metal and organotoxin accumulation and subsequent upward migration of these substances in the food chain.
Earthworms derive their nutrition from organic matter in a wide variety of forms. So far plant matter (various forms, fresh-decayed), protozoans, rotifers, nematodes, bacteria, fungi and decomposing remains of other animals are known to be worm food.
Earthworm cultures can be obtained commercially. In South Africa, many households and even hotels are using earthworms to convert normal kitchen waste into compost. Once they are established, these cultures do not smell or attract flies. As a food source for koi, these cultured worms may be the best option because it is fairly hygienic and the worms can also be gut-loaded to increase the nutrient content.
Taking the above into consideration, earthworms are a readily available treat for koi that can be sourced commercially or from one’s own back yard. Various studies have been undertaken especially in Nigeria about the feasibility of replacing fish meal with earthworm meal in animal feeds. The results of these studies are very encouraging. Earthworms are perhaps the best food supplement for the hobbyist.
Can be cultured easily and is a great way to recycle kitchen waste
Earthworms are relatively inexpensive and easy to obtain
High in protein and little fat, so earthworms can be fed all year round
Worms can be “gut-loaded” for added nutritional value
Valuable source of minerals and trace elements
The possibility of heavy metal and organotoxin accumulation exists
Nutritional Value of Tadpole meal (Dried)
Crude Protein: 43.5%
Crude lipid: 11.3%
Crude Fibre: 3.8 %
Ash: 26.5 %
As a matter of interest, live tadpoles consist of between 70% to 90% moisture in bodyweight
Yes, I can see the frown, and yes, tests were conducted to determine the Nutritional value of tadpoles to replace fish meal in animal feed. Although very little data exists on the full nutritional value of live tadpoles, the analysis of dried tadpole meal can give an indication of the nutritional value when live tadpoles are offered to koi. Tadpoles referred to here, are tadpoles from frogs and not toads.
Tadpoles as a food supplement for koi is actually an acquired taste and not all koi will readily take them. When conditioned properly, koi will actively hunt them and will even hang around the waterfall waiting for them to be washed into the pond! Most koi keepers however, shy away from the idea of purposely feeding tadpoles to koi.
Tadpoles are easy to obtain from pools and puddles.
They may even find their way into a pond by themselves.
May carry disease into pond
Fish should be conditioned before they will take tadpoles
Tadpoles are a seasonal occurrence
Not all koi keepers will have the stomach to feed tadpoles to koi.
Nutritional Value of Crickets
The nutritional value can be greatly improved by feeding high quality diet and by “gut loading”.
The brown cricket (Acheta domestica) is also a popular food for a variety of pets and can be a valuable food supplement to koi. They can be purchased from pet stores in quantities of hundreds and in various sizes. The price of these critters and the amount of them that are needed to feed a koi collection is however prohibitive. The nutritional value of crickets depends greatly on what they are fed.
Crickets are easy to obtain in a variety of sizes
Available all year round
Can be kept alive for considerable time
Crickets are a good source of protein
Hygiene is not a problem
Very expensive to buy
A lot of crickets will be required to feed a koi collection
The list of live food as a supplement to a balanced dry food for koi is limited only by the imagination of the koi keeper and the availability at a specific time. Hobbyists can determine the type of supplement they would like to offer their collections after carefully considering the age of the fish as well as the nutritional value of the particular live food.
Last Updated on Sunday, 14 November 2010 14:00