Fish Ponds

The first problem that faces the amateur breeder is that of sexing the fish. In most fish the only sure way is to dissect them, but as this is not practicable you can make an educated guess. Koi Carp are easy to sex because the pectoral fins in the male are pointed and in the female they are more rounded. With all coldwater fish the female is broader across the beam. Mature male goldfish sometimes develop little tiny white modules on the leading edges of their pectoral fine during the breeding season. In all species the male fish will chase the female prior to spawning and a deft scoop with a net will sometimes mean that they can be separated. This must be done to make sure that the female remains full of eggs and is ready for spawning. Rough handling must be avoided as this will cause the eggs to released prematurely.

Spawning will take place early in the morning, last for several hours and can often be induced by pumping cold water into the pond a few hours previously. Somewhere for the fish to lay their eggs such as a spawning mop made out of wool, or bundles of oxygenating plant should be provided. If it is mid summer, water hyacinths will be available which are much favored in Japan.

Prior to spawning and afterwards the fish should be fed good quality food, especially live foods such as maggots, washed earthworms, bloodworms etc. Commercially, fish are brought into breeding condition by hormonal injections, then the eggs and sperm are removed from the fish by hand and gently mixed together to fertilize the eggs.

It is probably easiest to spawn the goldfish related species in an aquarium because after the eggs have been laid the adult fish must be removed otherwise they will eat the eggs. Goldfish may lay 1000 eggs, or more and if left to their own devices in the pond only a dozen, or so are likely to survive to maturity. Even after the fry have started growing they must be kept separate from larger fish for at least the first year.

The eggs may be kept warm in an aquarium by the use of a small heater and will take a few days to hatch. After hatching the fry will hang on the side feeding off their eggs sacs far a couple of days and then they should be fed with either a proprietary fry food, or Infusoria. This can be prepared by pouring some boiled water over some lettuce leaves and leaving it to stand. After a day or so the water will go cloudy and then clear. This is when the infusoria solution is ready. A fresh preparation should be made every 3 days to provide a constant supply.

As the fry get bigger they can be fed on newly hatched brine shrimps and then on powdered flakes. The tank must be kept clean and well oxygenated at all times. Many fry will die and must be removed, but hundreds will survive if looked after and they grow quickly so must be given plenty of space.

Goldfish fry will soon darken to a brown colour and may take a year or two to change to the true goldfish colour. Some goldfish never change colour and revert to the colour of a natural carp. These are said to be ferral carp. Shubunkins and Koi fry will show colour earlier, but the colours will change as they grow older until they become fixed. Goldfish need to be about 5 - 6 inches, or 15 cm before they will breed and Koi about 10-12 inches, or 30 cm. Golden Orfe also need be about one foot long, but Golden Rudd only need to be about 8 inches. Orfe will usually breed true, but Rudd vary quite a lot so when the fry are changing colour you must cull them killing the poorly coloured ones.

Breeding Black Moors, Fantails and the other fancy goldfish species is just the same as for ordinary goldfish. The main difference is that very few of the fry will make good specimens and you must start culling the fry as soon as possible to allow the others to develop. Black Moors may take a year, or so before they achieve the deep black colouration that they are well known for.

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