BREEDING Breeding koi About the author:
Dave Wolfenden started his career with an honours degree in Zoology and Botany at Reading University. After a further year within the aquatics industry he became a lecturer in Animal Management at Merrist Wood College in Surrey, specialising in managing and tutoring on higher education courses. Now a lecturer at Reaseheath College, Dave also acts as a Tetra Consultant for the Tetra Information Centre.
Part two
Last month Dave Wolfenden investigated the fundamentals of breeding koi, from selecting and sexing broodstock to managing the spawning process itself. Assuming that spawning has been successful, what happens next?
Oomo Showa spawning All pictures courtesy of Cuttlebrook Koi Farm
T One of the best
forms of filtration for such systems is
actually one of the simplest…
50 KOI CARP
he eggs (which are only about 1mm in diameter) from a successful spawning need to be removed from the spawning pond on the
spawning rope, or whichever medium is used. As we discovered last month, koi are pretty lacking in the parental care department and will readily eat their own eggs! Alternatively, if a dedicated spawning
tank or vat has been used, it may be possible to remove the parents and use the spawning system for hatching and growing on the fry. In any case, the hatchery needs to be reasonably large – about 500 litres is advisable.
getting it right There are some very important considerations
that need to taken into account at this crucial stage: firstly, water quality. The eggs and the
resulting fry are very sensitive to fluctuations in water quality. For this reason some form of filtration will almost certainly be necessary, unless provision is made to employ a constant trickle of clean water into the system. One of the best forms of filtration for such
systems is actually one of the simplest – the good old air-driven sponge filter. These ‘old school’ filters are very kind to the delicate fry but should, of course, ideally be established and inoculated with nitrifying bacteria prior to their use in the rearing system in order to prevent excessive spikes of pollutants. Fungus (Saprolegnia) can be a real issue in
these systems and, once it’s taken hold, it’s rapidly capable of wiping out the entire batch of eggs. The addition of 0.2mg/l of malachite green can help to keep it in check (of course, when performing water changes, the level of malachite will need to be maintained). Aeration should be employed. Placing
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