Japan Day 2018
Japan Day 2018
KoiNet will be partaking in the Japan Day 2018 at Oude Libertas, Stellenbosch, tomorrow, 17th March. We hope to see all our friends and clients from Cape Town and surrounds there.
Come get the Japanese vibe at Oude Libertas this Saturday.
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The Making Of Colour
In a colourful world
While the morphological variation was important in the creation of koi as they are today, the expression of color is certainly central to defining koi as ornamental. It is true to say that without colour koi would never have developed. Skin pigment cells produce the various colors. Erythrophores and xanthophores contain carotenoid pigments and produce various shades of red or yellow. Melanophores are black and contain melanin.
Mutag BioChip vs Kaldnes K1
Mutag BioChip vs Kaldnes K1
In a recent study, Bassin et. al. (2016) assessed the activity of the suspended and attached biomass on two types of moving-bed biofilm carriers under identical conditions. The moving-bed biofilm reactors were loaded with K1 (MBBR1) and white Mutag BioChip™ (MBBR2) and evaluated at different pollutant loads.
The Angle of View
The Angle of View
In our hobby the body shape of a fish tells us much. The concerned hobbyists try to gauge the sex, the age, future potential and quality from what they see. When looking at photos however, it is easy to form the wrong impression. Be careful to judge too quickly.
When viewing photos of fish, one must be aware how serious the angle of view can effect the photo.
Jumping and swimming speed
Jumping fish and swimming speed
Many koi owners have experienced a fish flapping on the lawn because it jumped out of the water. Many have spent fruitless hours trying to revive these suffering fish in the hope of a miracle happening. We want to blame someone for this mishap and are quick to find the culprit, usually a protection net that was carelessly closed over the tank, or worse, failure to use the net at all. They call that negligence.
There may be other reasons for fish jumping. Rushing, bubbling water is one. A waterfall, or water bubbling from air stones or return pipes dangling near the pond edge ...
Diffusion Depth
Media and the Diffusion Depth of the Biofilm.
The diffusion depth presented impacts on the evaluation of removal rates and treatment performance of MBBR carriers (biofilm media). Dr. Markus Geiger and Bernd Rauch from Multi Umwelttechnologie AG discuss important aspects to consider.
This technical article points out the importance of oxygen diffusion depth of the biofilm. The ideal requirements can be fulfilled by thin, disc-shaped and porous carriers. This has impact on the design of biological filters irrespective their application whether for wastewater treatment, recirculation aquaculture systems (RAS) or domestic koi ponds.
Showa or Sanke
Showa or Sanke, what is in a name?
By Jim Phillips (SAKKS)
What's in a name? That which we call a rose,
By any other name would smell as sweet
William Shakespeare 1595 Romeo and Juliet. Act 2 scene 2.
RAS Systems - Super Filter Media
The Mutag BioChip™ media for moving bed biological filters.
Aquaculture professionals, breeders and koi communities use Mutag BioChip™ as biofilter media for best water quality and large savings on OPEX
The Mutag BioChip™ speeds up pond filters with 3,000 m² of active surface area per m³ of filter media for the steadily growing nitrifying microorganisms for reducing the ammonia which is produced by the fish.
Show Water Management
Ever since I got involved with koi shows the seeming endless chore of water changes was a concern of mine. Not only was it a labour intensive task requiring constant attention and management; it also was a very wasteful act. On more than one occasion we
All about Size
Growth dispersion
This article is for carp and koi breeders of all persuasions and skills. The experienced farmer who wants to improve his breeding returns and the first-time novice breeder who do not know how to react to this observation. We revisit ‘ancient knowledge’ to explain common observations of fry when indulging in breeding, whether professionally of for pleasure.
It is a common occurrence to observe a wide range of fish size when the fry pond is harvested. Some fish would be extraordinarily large in relation to the average, and many a neophyte farmer will pride themselves when finding some 15-cm fish amongst their harvest of 30-day old juveniles for their first culling.
This fast growing fish are called “shooters”, “shoot carp” or “tobi-koi“ and seen throughout the industry of koi or carp breeding. Often tolerated and ignored. Often boasted about. Often thinking to breed with the shooter. Mostly not knowing the reason and the negative effect it can have on the rest of the fry population. Also, not realizing it is a sign of improper pond management and that it can be corrected with intervention by the farmer.
Try to understand the graph below:
Figure 5.3 Frequency distribution of the body length of 20-days old koi fry to illustrate the appearance of fast growing tobi-koi. Average size 9.47 mm, coefficient of skewness +1.532. (Redrawn from Nakamura and Kasahara, 1955, p47)
The appearance of tobi-koi was studied thoroughly by Japanese scientists, Nakaroku, Nakamura and Shogoro Kasahara who dedicated seven years of research to the phenomenon. The results were summarized by G W Wohlfarth (1977) who should also be thanked for getting the original Japanese research articles translated into English for consumption in the rest of the world and ending the agony of breeders in breeding with these shooters in the hope of raising jumbo koi.
Figure 5.4. Typical growth dispersion due to poor fry pond management. The large fish is 150 mm and the smallest 35 mm. More than 4 times longer and a mass of about 240 times heavier. To look at this discrepancy in another way: the large juvenile had to eat the food of 240 small ones to get that big.
The frequency distribution of the size of a koi population in a pond is normally skewed and the width of the distribution may be affected by conditions in the pond. The skewness of the distribution is an indication of asymmetry from the normal, bell shape, distribution. The investigations of Nakamura and Kasahara (1955, 1956, 1957 and 1961) was summarized by Wohlfarth (1977) as follows:
- The frequency distribution of length for a population of newly hatched fry is symmetrical, but skewness is first observed at 20 days of age, when they start eating natural food.
- The length frequency distribution of individuals grown separately is symmetrical, but when a number are grown in the same container, growth dispersion is observed.
- The appearance of tobi-koi in a group is suppressed by adding a few slightly larger individuals.
- When removing the few larges individuals from a group to restore symmetry, skewness is restored soon after. Secondary skewness becomes less with the age of the fish.
- Quantity and quality of food are primary factors determining the degree of skewness. Insufficient food results in increased skewness.
- Small, same sized food prevented the appearance of shoot carp
- Smaller sized food results in decreased skewness.
- Occurrence of shooters is greater when survival is low.
- More food equate to less shooters and better average growth
- Stocking densities, per se, did not result in skewness. If feed is proportionally increased, degree of skewness remains the same.
Nakamura & Kasahara concluded that the skewness is due to the competition for food and peculiar to carp and koi due to their eating habits. Koi fry have an aggressive eating habit. It seems to “attack” the food particle. They also illustrated that goldfish fry that prefer phytoplankton and algae, and generally smaller prey than koi, do not exhibit the shooting phenomenon. Koi fry prefer zooplankton and Clandocera of a particular size but in its absence, will take a wide variety of other natural foodstuff as it grows up. The shooter phenomenon seems to be inherently tied to competition for a food particle of a particular size. If there was any genetic foundation it could be in some degree in the aggressiveness towards eating, thus far there is no evidence of that.
That the appearance of shooters is greater when survival is low could well be because of cannibalism. Cannibalism appears to be tied to the (density fry) : (density adequate feed) ratio when larger offspring develop 'n taste for its smaller siblings drastically reducing the population.
Although the researchers showed that the appearance of shooters was not a function of stocking density and did not exaggerate the skewness when the food supply was proportionally increased, it still remained a factor when trying to extrapolate what happens in a fry pond under normal conditions. The slightly bigger fry eating a slight larger food can effectively remove all the adult pray animals before moving on to a bigger or different type of food morsel. Those fish that slightly lag in size, that may be a little slower in development or a little less aggressive will find by the time they switch from larval to adult Clandocera will fine all the adults gone and also the source of offspring gone. They simply run out of the food in their “prey niche”. In this manner the bigger fry increasingly consume more, leaving less for those who lags behind grow progressively slower. By removing the source of a new generation of prey, the whole supply chain collapses. So, while we can say it is not a function of stocking density, it is in the case of semi-intensive systems a function of pond productivity and the ability of the pond to provide sufficient food organisms for its population as they grow up. As the stocking density increases the ability of the farmer to provide sufficient food to the pond becomes increasingly more difficult and it becomes more difficult to predict and manage.
Having 25% of the harvested fish outside the modal group and responsible for more than 60% of the food consumed as the graph in Figure 5.5 suggests, is clearly not good pond keeping. Considering that the shooter group will be subject to the same culling criteria it can be seen that it results in poor economics due to less efficient use of food and reduced income due to reduced size. It is important for the koi farmer to recognize that it is the supply of sufficient food of the correct size during the first twenty days of stocking the fry pond, that is required to grow all the individuals to their best potential. It is however imperative to maintain the supply of available food for the fry throughout the 30 to 40 days in the fry pond.
Breeders are advised to pay close attention to these findings and consider how they should adjust their fry rearing practices to minimize the effects of growth dispersion. It will be well worth the effort.
(Extracted from Chapter 5. Rearing koi. In Koi Culture by Servaas de Kock and Ronnie Watt.)
References:
Nakamura, N. & Kasahara, S., 1955, A study on the phenomenon of tobi-koi or shoot carp. I. On the earliest stage at which the shoot carp appears. Bull. Jpn. Soc. Sci. Fish., 21: 73-76 (translated in Bamidgeh, 29: 41-44, 1977).
Nakamura, N. & Kasahara, S., 1956, A study on the phenomenon of tobi-koi or shoot carp. II. On the effect of particle size and quantity of the food. Bull. Jpn. Soc. Sci. Fish., 21: 1022-024. (translated in Bamidgeh, 29: 44-47, 1977).
Nakamura, N. & Kasahara, S., 1957. A study on the phenomenon of tobi-koi or shoot carp. III. On the results of culturing the modal group and the growth of carp fry reared individually. Bull. Jpn. Soc. Sci. Fish., 22: 674-678. (translated in Bamidgeh, 29: 48-52, 1977).
Nakamura, N. & Kasahara, S., 1961, A study on the phenomenon of tobi-koy or shoot carp. IV. Effects of adding small number of larger individual to the experimental batches of carp fry and culture density upon the occurrence of shoot carp. Bull. Jpn. Soc. Sci. Fish., 27: 958-962. (translated in Bamidgeh, 29: 53-56, 1977).
Wolfarth, G. W., 1977, Shoot carp. Bamidgeh, 29(2): 35‑40,
Choice of water Testing
We are all like that. We want the best that our money can buy. Sometimes we simply want the best car to drive out from behind our walled properties into the street. But when we sit back and consider the options, our senses override our pride. The money in our pockets speaks.
Biology and Ecology of Carp - New Book
This new book may be about carp, but if we remember that Nishikigoi is really ennobled carp, it has information of interest to all of us.
Biology and Ecology of Carp
Editors Constanze Pietsch and Philipp Hirsch
Acidification - Revisited
All of you who are heavily feeding your fish will know the problem of acidification of your pond. Also called "acid creep", when the pH drops so low that it affects the appetite of your priced collection and rendering the biological filtration virtually non-effective. You might even find white patches developing on their fins and body. The fish normally become lithargic and listless.
So you jump to the old "bicarb" packet to solve the problem and your battle with "perfect" water starts all over again. Because just when you think you have it right, off it goes again.
StabHi
StabHi Organic Substrate are pebbles that has been tested to stabilize the pH while biological nitrification processes continue.
Used StabHi to increase the pH, alkalinity and hardness of aquaria and fish ponds all at the same time. The biological processes in aquaria and fish ponds need the correct levels for pH and alkalinity to function properly. Equally important is to maintain the hardness by adding calcium and magnesium ions.
