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Thread: Pond depth

  1. #1
    Senior Member Rank = Sansai JimJones's Avatar
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    Pond depth

    I know this is opening up a can of worms.

    might as well called the thread " multibay or Nexus ha ha ha"


    I have read on here that ponds below 2m can cause swim bladder issues to the fish.

    For extra gallonage I am planning a 2.2 m deep pond but can take it to 2m if necessary as it is boxweld and i can trim off the excess.

    anyone have an experience in this mattter

    thanks

    Jim



  2. #2
    That myth won't go away no matter how many times it's explained.

    Carp evolved in lakes that were often (usually) deeper than 2m. If they suffered from decompression sickness or swim bladder problems if they were foolish enough to venture to the bottom of the lake without observing a full decompression procedure as they swam to the surface, the species would never have survived to evolve.

    The myth is the result of incomplete understanding of the risks of injecting air into water under pressure. When we aerate water, we don't just add oxygen, we are adding all the gasses that comprise the atmosphere. If air is injected under pressure, the area local to the injection point will become supersaturated with oxygen and with the nitrogen that also is injected (other gasses will also be injected but only oxygen and nitrogen are important so we can ignore those).

    If koi "breathe in" supersaturated gasses at any depth then, as they swim up into normally aerated water, the gasses will expand in their bodies. Oxygen is a metabolic gas so it will rapidly be used and will not accumulate in a fish's body. However nitrogen isn't required by any cell so it will expand and form bubbles in the body which won't dissipate and will therefore cause problems similar to the decompression sickness that divers can suffer from if they breathe air at depth and then surface too quickly.

    Personally, I can't imagine that ordinary air pumps could inject air at a sufficient pressure at depths greater than a couple of meters that would cause a problem but a good precaution for anyone who wants a deep pond is to not have any airstones at depths greater than about 2m.

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  4. #3
    Quote Originally Posted by Manky Sanke View Post
    That myth won't go away no matter how many times it's explained.

    Carp evolved in lakes that were often (usually) deeper than 2m. If they suffered from decompression sickness or swim bladder problems if they were foolish enough to venture to the bottom of the lake without observing a full decompression procedure as they swam to the surface, the species would never have survived to evolve.

    The myth is the result of incomplete understanding of the risks of injecting air into water under pressure. When we aerate water, we don't just add oxygen, we are adding all the gasses that comprise the atmosphere. If air is injected under pressure, the area local to the injection point will become supersaturated with oxygen and with the nitrogen that also is injected (other gasses will also be injected but only oxygen and nitrogen are important so we can ignore those).

    If koi "breathe in" supersaturated gasses at any depth then, as they swim up into normally aerated water, the gasses will expand in their bodies. Oxygen is a metabolic gas so it will rapidly be used and will not accumulate in a fish's body. However nitrogen isn't required by any cell so it will expand and form bubbles in the body which won't dissipate and will therefore cause problems similar to the decompression sickness that divers can suffer from if they breathe air at depth and then surface too quickly.

    Personally, I can't imagine that ordinary air pumps could inject air at a sufficient pressure at depths greater than a couple of meters that would cause a problem but a good precaution for anyone who wants a deep pond is to not have any airstones at depths greater than about 2m.


    At the deepest point of my pond its about 2m. I have 4, 8 inch air discs at that level and 1 slightly higher up running off an EA130. I didn't think it would have been an issue but I guess it's something I don't understand that I need to look into.

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  6. #4
    Quote Originally Posted by kikokuryu John View Post
    At the deepest point of my pond its about 2m. I have 4, 8 inch air discs at that level and 1 slightly higher up running off an EA130. I didn't think it would have been an issue but I guess it's something I don't understand that I need to look into.
    It's always best to ask John and Manky's probably the best one to ask on here

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  11. #7
    Senior Member Rank = Sansai JimJones's Avatar
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    thanks manky

    used to work as a scuba instructor so I am fully on board with your great advice. Never thought I'd be applying Boyle's ,Charle's law and henry's law to my koi though ha ha ha

    I guess I'll have to put the fish on computers instead of using the tables to give them extra bottom time !

    I will have a spindrifter though but i am not going to put a lot of air through it. as I have a waterfall that is fed via a shower.

    thanks

    Jim

    Ps would 2.2 meteres depth be ok or shall i go with plan B and level off at 2m and trim my boxweld?
    Last edited by JimJones; 23-05-2019 at 11:32 AM. Reason: needed more facts on a PS

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  13. #8
    I would go for 2.2 metres to get the extra volume Jim, and I wouldn't worry about using airstones at the full depth or even an aerated bottom drain dome if you wish.

    Of course you may wish to be cautious and put a high visibility line at 2 m depth with a warning notice that your fish mustn't go beyond that limit unless accompanied by a dive buddy.

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  15. #9
    Senior Member Rank = Sansai JimJones's Avatar
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    ha ha ha thanks mate

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  17. #10
    Quote Originally Posted by Manky Sanke View Post
    Of course you may wish to be cautious and put a high visibility line at 2 m depth with a warning notice that your fish mustn't go beyond that limit unless accompanied by a dive buddy.
    The problem is you'd have to have the sign written in English, Japanese and Hebrew as you never know what koi you might add in the future

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