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  • Results 1 to 3 of 3

    Thread: Goldfish Max Size - Personal Experience Only. Thank you!

    1. #1
      TJeep's Avatar
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      Jun 2021
      North Carolina

      Question Goldfish Max Size - Personal Experience Only. Thank you!

      For reference I have a 450 gallon heavily planted pond with a 3000 gallon filter on it that cycles the pond water 5 times every hour. No UV light. I clean the bottom weekly and do water changes that back flush the filter every 2-4 weeks. Water is always crystal clear. My ammonia, nitrates and nitrites have always tested zero since setup. I feed the fish small koi/goldfish food 1-3 times a day, but only a very small amount each feeding making sure each fish gets at least some food. My oldest single tail goldfish are approximately 2 years old and 6-7" long.

      I keep reading online that single tail goldfish can easily get to be 12"+ but I've also seen online that they usually get to be around 7" long. I've read that they also are fully grown around year 2, but also that they never stop growing. I've also read they will limit growth to the size of their tank. I've also read that it is a myth they limit their growth based on tank size.

      So... Given that the internet is contradicting itself I would like to know what size your single tail goldfish actually achieved and around what age they achieved it. I do understand the irony of asking this on an "internet" forum. Saying that, please limit replies to actual personal experience with only your personal goldfish. Pond size and feeding info might also be helpful, but not required. Thank you!!

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    2. #2
      mjfromga's Avatar
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      Feb 2017
      My system is close to the size of yours. No plants. Filter system not that large. Water change regimen isn't consistent like yours. Water always tests 0/0/0 though same as yours. Water almost always green most of the year. Almost never clear, not even most of winter. Large outdoor air pump and two large airstones producing a good deal of surface agitation. I don't keep many single tails - but mine grow to about the size of yours or maybe slightly larger but never 12+ inches. I've only seen single tails in giant Koi ponds grow huge like that. Goldfish can inhibit their growth with a hormone to keep them from outgrowing their environment. I don't feed like you do though. My fish are fed once per day in warm months and twice per day in hot months. I never feed very much. Sometimes they don't get fed at all because I get busy... and in cool and cold months, I don't feed them at all.
      Last edited by mjfromga; 4 Weeks Ago at 08:17 AM.

    3. #3
      *Ci*'s Avatar
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      Nanaimo, BC Canada
      I have some older goldfish that have always been in large filtered ponds and fed abundantly. The largest and oldest is a Shubunkin at 14 yrs and he is about 9” of body length, and has been this size for a number of years, so I believe he has stopped growing. One of the problems is method of measurement. He has a very long tail, so some would say he is over 12”. This is why koi are measured from nose to penduncle and the tail length is not counted (especially important for butterfly koi). This avoids misleading measurements.

      I think that the limiting factor for growth is most likely water quality rather than a natural hormone function in the fish. As they grow larger and are kept in small environments like fish tanks, most people cannot keep up with their requirements and the fish stunt or die prematurely. Build up of hormones in the water would be a part of this, hence the idea that the fish is regulating itself.

      If a goldfish or koi is kept in abundant, clean, well filtered and refreshed water for it’s lifespan it will grow at a rate dictated by temperature and feeding regime and stop growing when it has reached it’s genetic potential. Some goldfish may have the potential to reach over 12”, probably the less refined orange or wild coloured commons, while other varieties that are more colourful and genetically manipulated by humans stay under that size (much like koi).

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