Surprising koi growth trials

Surprising Koi, and carp, of course, are well-known for their wide-ranging appetite. If something is edible, carp are likely to eat it. Nevertheless, being carp, which are ideally equipped for feeding along the bottom of ponds and lakes, much of their natural diet consists of plants and plant debris.It therefore comes as a bit of a surprise to learn that a study carried out in India has shown that it is not phytoplankton (i.e. free-floating microscopic plants) that produces the best growth rates in young koi, but zooplankton (i.e. floating or swimming microscopic animals). In fact, it is not just one study, but four, that have shown this to be the case.The trials were carried out by scientists from the University of Bengal who wanted to assess seasonal influences on the growth and production of young koi. Four trials were therefore carried out to coincide with four major seasonal conditions: winter, summer, monsoon and post-monsoon.Each trial lasted for eleven weeks, during which period some of the koi were fed on live zooplankton, while others were fed on micro-organisms resulting from the addition of poultry manure or cow dung to their water. Another group (the control) was fed on a commercial diet with a crude protein content of 32 per cent.When the results were analysed, it was discovered that koi fed on live zooplankton gained significantly more weight than those fed on any of the other diets. They also showed a lower incidence of deformities and higher survival rates. Perhaps surprisingly, those fed on the commercial diet fared worst, exhibiting the highest incidence of deformities and only half the weight gain achieved by their zooplankton-fed counterparts. This particular commercial feed obviously lacked some of the essential compounds required for optimal growth.The findings are significant in several ways. From the commercial viewpoint, the most significant is perhaps that the use of live zooplankton can reduce the period required for young koi to attain marketable size by about one half. When this is added to higher survival rates and fewer deformities, the advantages of using a diet based on live zooplankton during the early growth stages may well outweigh any disadvantages such as price when compared to other feeds.For the full content of the paper in which these trials are described, please consult: Jha P. Barat S and K Sarkar (2006) – Comparative effect of live food and manured treatments on water quality and production of ornamental carp…