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  1. #1
    Senior Member Rank = Yonsai Twhitenosugar's Avatar
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    Growing jumbo sized koi unheated

    I know genetics plays a big part in things, but say i had a fish that had the right genetics, and i had great water quality and plenty of filtration and plenty of good quality food, is it possible to grow fish to jumbo sizes in an unheated pond?

    Is it the case that heating the water just means they grow big faster, so going unheated means they will get to the same size but it takes longer to do so.

    Or is it more the case that you really need the fish to grow big when they are in their prime growing years before their growth starts plateauing out? So going unheated means that won't necessarily attain their full growth potential?

    I'm interested in what people's experiences are on this, as I'm realtively new to this koi lark.

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    Last edited by Twhitenosugar; 04-07-2020 at 07:24 PM.
    12,500L fibreglassed raised pond with window

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  3. #2
    that's a good question and I'll be interested to hear what people think. Based on little experience and some reading my gut feel is yes but probably not to maximum potential.
    If you consider the japanese breeders, they select on genetics then chuck them in a mud pond to grow over summer - I image the pond water will be quite warm but certainly not hot and there are obviously other factors to consider, like feeding.....

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  5. #3
    Extreme Koi Member Rank = Yonsai phil45's Avatar
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    My view is that genetics play a large part in it as some koi simply do not achieve any great size , the ones i have raised from a known breeder of good size parents have ended up large fish , even though i do not heat they get there in the end it just takes longer ..........and if you want size avoid doitsu

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  7. #4
    Senior Member Rank = Yonsai Twhitenosugar's Avatar
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    Quote Originally Posted by phil45 View Post
    My view is that genetics play a large part in it as some koi simply do not achieve any great size , the ones i have raised from a known breeder of good size parents have ended up large fish , even though i do not heat they get there in the end it just takes longer ..........and if you want size avoid doitsu
    Glad to hear it. When you say big, how big are we talking? I ask as it seems to me that koi in most conditions can be grown up to the 60 - 70cm mark. But it seems to me quite rare that they grow past that mark in unheated scenarios and seem to plateau off growth wise.

    That's interesting that you say avoid Doitsu if you want them big.

    As mirror carp tend to grow bigger (often guttier if that's a word) than common carp in carp fisheries.

    I suppose the traits of 'normal' carp can't always apply to koi, as koi are so heavily selectively bred.

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  9. #5
    Senior Member Rank = Hassai Sim's Avatar
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    I think if you had everything else right then the koi would grow to good size but I think the overall growth would be slightly down.
    if it has the potential to grow to 90cm I think you may break 80cm.

    its not just the heat, it’s keeping the fish well and reducing stress, as the temp warm in spring or cools in winter it fluctuates and will stress it therefore reduce any growth.
    This is on top of the cold period that you weren’t feeding.

    I think for me this is the main reason for heating, reduce the stress and keep the koi healthy so parasites and treatments are not needed as often.
    These things may be small but they will all play a big part in growth, so all year temp is a massive benefit.

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  11. #6
    Quote Originally Posted by phil45 View Post
    My view is that genetics play a large part in it as some koi simply do not achieve any great size , the ones i have raised from a known breeder of good size parents have ended up large fish , even though i do not heat they get there in the end it just takes longer ..........and if you want size avoid doitsu



    I'm not sure the 2 guys in this video would agree with that. Skip to the 2 min mark


    https://youtu.be/51dC8JXSus4

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  13. #7
    Senior Member Rank = Yonsai Spongebob's Avatar
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    As a ex carp fisherman I’d just say warmer countries produce much bigger carp, and the Japenese breeders fish are warm all year round (heated in winter, combined with very warm and humid summer. Heat = Big I’d say.

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  15. #8
    All the dodgy big fish stocked in lakes these days seemed to be selected for their genetics then theyíre fed shedloads of food. (Or have a look at EuroAqua for some serious massive Mirrors)
    Same as rainbow trout even 20+ years ago. My old Dad caught a British record rainbow back then which had been raised this way then stocked into the millpond at his club lake, he got loads of grief at the time but didnít claim it (rightly imo). Itís still an impressive fish even now (itís been mounted) but ďfakeĒ. I digressed a bit there sorry.
    Anyway, itís all about the
    Genetics
    Water
    Heat
    As much food as you can throw in
    Filtration to cope with the above.

    Carp of all varietyís are just swimming pigs lol


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  16. #9
    Senior Member Rank = Hassai hippo's Avatar
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    Having an unheated pond , I find the fish don't feed the same amount each day . The weather has been so erratic this year , its bound to affect the feeding levels . So as a consequence , you wont get the same growth .

    I don't know if anyone follows " koi diaries " on you tube (cant get the link right now - I`m at work) , but the guy on there has just installed a heater , to try and improve growth , so might be worth following him , to check how he gets on (no ,Im not on a commission)
    Colin

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  17. #10
    Senior Member Rank = Yonsai Twhitenosugar's Avatar
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    So based on what most people are saying so far, it seems the consensus is that going unheated will prevent a fish fron attaining it's biggest potential size, rather than it just taking longer to get there - even if the genetics, water quality and availability of good food is all there.

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  18. #11
    Senior Member Rank = Yonsai Twhitenosugar's Avatar
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    Quote Originally Posted by hippo View Post
    Having an unheated pond , I find the fish don't feed the same amount each day . The weather has been so erratic this year , its bound to affect the feeding levels . So as a consequence , you wont get the same growth .

    I don't know if anyone follows " koi diaries " on you tube (cant get the link right now - I`m at work) , but the guy on there has just installed a heater , to try and improve growth , so might be worth following him , to check how he gets on (no ,Im not on a commission)
    I'll have to check that out. Cheers.

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  19. #12
    Senior Member Rank = Yonsai Twhitenosugar's Avatar
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    Following on from the theme of growing jumbo koi. I was wondering which breeders have a reputation for growing certain types of koi very big.

    For example I've heard that Isa have a reputation for producing big Showas, Sakai for producing big Kohaku and Hirasawa for producing big Chagoi.

    What other breeders are known for producing jumbo sized fish. When asking this, I appreciate that just because a breeder has a reputation for producing good fish of a certain type, it's not a guarantee that everything they produce will be big or have a perfect pattern.

    I'm just interested in what the various breeders are best known for really.

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