Spawning Goldfish or Koi in Aquaponics

Many people ask me if there goldfish or koi will breed in an Aquaponic system. The short answer is if conditions are right your fish will always spawn all by themselves without much assistance from you. That said, you can help to trigger them to spawn and if they do you may want to get ready for the thousands of eggs and young fry that will hatch.

It doesn’t really matter if your fish are in a pond or if they are in a fish tank or IBC tank as fish will spawn regardless. Just keep on eye on your fish. If you notice them swimming rapidly around chasing each other than at that point you can be sure they will be spawning within an hour or so. If you don’t want to keep any young then just let them do their thing and some may survive however the vast majority of eggs will be eaten and few if any eggs will survive.

 If your deliberately attempting to spawn your fish then there are a few basic principles you will need to understand to help your fish spawn and to ensure that the majority survive:goldfish fry in Aquaponics

Select healthy fish of the variety you want to breed.  Make sure that they are of high quality to make sure that they will spawn good quality offspring. Remember that the ideal months to start breeding is between October to March in Australia as the weather warms.

Size – The larger the fish the more offspring will survive. Ideally your fish should be about 25 cm (10in) in length to ensure that they are sexually mature. The ideal Koi or goldfish male for breeding should be 3 to 5 years old, while a 4 to 6 year old female is best, being at its prime. 

Specimens chosen for breeding need to be conditioned for a year.  The best combination is two males to one female, a “ménage a trois”.  You need to put them in a separate “spawn pond or IBC tank” to ensure good genetics. This also helps reduce the likely hood of other fish just eating the eggs as they are fertilised and deposited around the tank or pond.

Setting up the location. There are several things that the fish need in order to spawn successfully.  The following needs to be ready and in place as soon as the Koi or goldfish are ready to spawn.
•    Aquatic weed habitat or medium or a place where fish they can lay their eggs. Artificial medium can be used if water plants are unavailable. In Aquaponics I grow water cress in the water and fish seem to spawn on it quickly without an issue;
•    Privacy – the newly hatched fry, being unable to swim yet, need a safe and secure place where they can hide;
•    Top quality water and correct pond temperature. You don’t want the water to fluctuate too much. Adding a heater for a week will help the young fry to grow and hatch quicker.

Gold fish fry in AquaponicsEggs:  You need to separate the eggs from the parents because they can be eaten pretty fast.  After spawning, and after the Koi or goldfish have been removed, treat the pond or tank with malachite green to prevent fungus from forming on any infertile eggs. Or if you don’t wish to use it get some tweezers and pluck out all the unfertile eggs. Fertile eggs will be a yellow colour and unfertile eggs will be white and will develop fungus. Maintain the temperature at 23oC and wait a couple of days for the fry to hatch.

Hatching:  After hatching, let the fry pass without feeding for 3 to 4 days.  Afterwards, bring them a very good source of abundant food. I add a cup of algae as it contains micro nutrients they need. About 27 degrees is the ideal temperature for growing fry.

Feeding fry: Take note that they still do not have any developed taste buds, so they can only detect food by sight alone; thus, they need to have food all around them.  For the first day or so, hardboiled egg yolk is the ideal food but it may lead to poor quality water if it’s not all consumed. Another good food source is brine shrimp, especially when the fry are about a week old.  After that, you can start feeding them a mash diet of power fish food rubbed between your fingers.

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