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Thread: Koi Stocking Density Equation

  1. #1
    Oyagoi Lam Nguyen's Avatar
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    Koi Stocking Density Equation

    There has been a lot of discussion about koi stocking density and the generally accepted knowledge is one koi per 1,000 gallons of pond water, although there are hobbyists who have had good growth results with a stocking density of as low as one koi per 500 gallons. By good growth results, I am implying koi that reaches 28+ inches in 5-7 years. I have been thinking about this topic for a while since this knowledge will directly affect the size of my next pond. While there are many parameters that determine growth rates, I was wondering if we keep these entire parameters constant, whether we could come up with a hypothetical equation that would determine stocking density.

    Constants these are parameters that must be present for optimal growth
    - Genetics have to come from jumbo oyagoi & have jumbo bone structure
    - Sex females tend to be more imposing
    - Age younger koi will grow faster than older koi
    - Water parameters soft water with TDS < 100 and pH between 6.8-7.2
    - Feed 4-6 small meals of high quality growth food daily w/ fresh vegs & fruits
    - Temperature 75-80 degrees F preferably

    Correct me if I am wrong, but my observation is that most people with a stocking density of 1 koi per 1,000 gallons have a pond turnover rate of approx once per hour. They also change about 15% of their water once per week. So, my question is, if we increase the pond turnover rate to once every 30 minutes and change 30% of water per week, then can we double the stocking density to one koi per 500 gallons? This means that, given that all the above-mentioned parameters are constant, koi stocking density is directly related to turnover rates and water changes. Obviously, when we turnover the pond from once every one hour to every 30 minutes that we have to have twice the amount of filtration. What do you guys think?!

  2. #2
    Oyagoi Eugeneg's Avatar
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    Correct me if I am wrong, but my observation is that most people with a stocking density of 1 koi per 1,000 gallons have a pond turnover rate of approx once per hour. They also change about 15% of their water once per week. So, my question is, if we increase the pond turnover rate to once every 30 minutes and change 30% of water per week, then can we double the stocking density to one koi per 500 gallons? This means that, given that all the above-mentioned parameters are constant, koi stocking density is directly related to turnover rates and water changes. Obviously, when we turnover the pond from once every one hour to every 30 minutes that we have to have twice the amount of filtration. What do you guys think?! [/quote]

    If that formula applied then if you had 15min circulation you would have 4 times the stocking rate. I t depends a lot on your filter media I am sure that you might gain a little in some instances but not much. It would be more important to isolate the solids as quickly as possible greater flow would make it more difficult. There is a very big diffrence in type of filtration such as baki showers or chamber filters. May be Steve and Larry can give us their opinions
    Regards
    Eugene

  3. #3
    Daihonmei PapaBear's Avatar
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    To tell you the truth I think Eugene touched on one of the most important points to ponder. Not all forms of filtration process wastes in the same way and that would make a huge difference in stocking densities and turnover rates. Flow rates that would work superbly for a Nexus might well be a miserable failure to a Bakki shower or Bubble Bead system on the same pond.

    We had a good discussion last year over at the shack about this and sort of came to a "happy medium" for a responsible baseline. Starting out with 1000 gallons before adding even one Koi and then for each Koi adding an additional 500 gallons ASSUMING that the pond was properly designed and filtered. Circulation rates beyond 1.5-2X per hour sound good, but there comes a tipping point of diminishing returns in my opinion. In most cases the dwell time for settlement and biological contact would tend to go south pretty quickly and could well cause water quality to go in the wrong direction. Water changes of 30% once per week can also introduce instability to the water and have a negative effect on fish and filters.

    To improve stocking capacity a flow through would be a safer and more stable method to maintain water quality in my opinion as additional fish could be accompanied by a commensurate increase in fresh water intake. That way the filtration and pond don't see weekly swings with large changes but are maintained in a steady condition at all times.

    If I'm not mistaken Momotaro runs his flow through discharge out the settlement chamber drains in order to continually purge solid wastes from the system. That would seem the most appropriate to me if I was wanting to maximize stocking density without sacrificing water quality.
    Larry Iles
    Oklahoma

  4. #4
    Oyagoi gcuss's Avatar
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    If the removal of solids was the heaviest factor in stocking density estimation, then a sieve would be the ultimate tool with it's ability to remove solid waste (within minutes of it's production) from the water column entirely... So a sieve on your bottom drain(s) and gravity feed your skimmer(s) through a sieve and your good to go?

    There's gotta be more to it...

    Grant

  5. #5
    Daihonmei MikeM's Avatar
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    Proper stocking is not determined by a formula. It is determined by the fishkeeper's goals, the pond design, the filtration system, the keeper's availability/willingness to engage in maintenance, water changes/ in-flows, and every other factor affecting the particular pond. Are there leaves falling in regularly? Do neighborhood raccoons use the pond for their personal hygeine?

    Even 1,000 gallons per koi is grossly insufficient in some circumstances. Would you want to take on the work involved in stocking a 10,000 gallon pond with 10 Chagoi measuring a meter apiece?

  6. #6
    Oyagoi Lam Nguyen's Avatar
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    Good points guys. So much for coming up with an equation/formula.

  7. #7
    Jumbo RobF's Avatar
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    A pond (and filter) is a system (just ask Steve Childers). This system can be described by a transfer function and hence can be described by an equation. Transfer functions are in the realm of Electrical Engineering, and the Filter Theory therein is pretty well understood, defined in the time domain and applied through the frequency domain. Engineers of the various types, Mechanical, Civil and whatnot have adapted Filter Theory to apply to their applications, with some success, at least in theory. In the case at hand, koi pond, the good news is that the primary forcing function is the water flow. The pumps, pipes, bends, valves, all have simple electrical engineering analogs, and in the simplest case one could even regard flow as steady (and a constant in the frequency domain). The levels of particulates might also be regarded as constant. However ammonia will fluctuate with feeding and is probably triangular or sinusoidal. And the bacterial response is likely some kind of exponential. The efficiency of the filters will vary as they foul. Waddington says that koi can never be a science. I am sure it could be, but science is kiwa not sashi.

  8. #8
    Honmei
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    Quote Originally Posted by RobF View Post
    A pond (and filter) is a system (just ask Steve Childers). This system can be described by a transfer function and hence can be described by an equation. Transfer functions are in the realm of Electrical Engineering, and the Filter Theory therein is pretty well understood, defined in the time domain and applied through the frequency domain. Engineers of the various types, Mechanical, Civil and whatnot have adapted Filter Theory to apply to their applications, with some success, at least in theory. In the case at hand, koi pond, the good news is that the primary forcing function is the water flow. The pumps, pipes, bends, valves, all have simple electrical engineering analogs, and in the simplest case one could even regard flow as steady (and a constant in the frequency domain). The levels of particulates might also be regarded as constant. However ammonia will fluctuate with feeding and is probably triangular or sinusoidal. And the bacterial response is likely some kind of exponential. The efficiency of the filters will vary as they foul. Waddington says that koi can never be a science. I am sure it could be, but science is kiwa not sashi.
    Yeah, what Rob said!

    Almost everything can be explained through mathmatics in sme fashion or another. The problem here is that there are many variables and it would take a PhD mathmatician to even begin to attempt a formula that would come close to being accurate.

    On the flip side, there are a number of succesful design criterias that are known to work for given stocking densities and husbandry techniques. Sometimes it is simply easier to replicate successful applications verses attempting to understand all of the intracies in order to apply such to another set of design criteria only to find out that a variable was unaccounted for and thus leads to a less than optimal result.

    Steve
    The views presented are my personal views and not that of any organization that I may belong to unless otherwise specified. [email protected]
    CKHPA

  9. #9
    Oyagoi Lam Nguyen's Avatar
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    ........We had a good discussion last year over at the shack about this and sort of came to a "happy medium" for a responsible baseline. Starting out with 1000 gallons before adding even one Koi and then for each Koi adding an additional 500 gallons ASSUMING that the pond was properly designed and filtered. Circulation rates beyond 1.5-2X per hour sound good, but there comes a tipping point of diminishing returns in my opinion. In most cases the dwell time for settlement and biological contact would tend to go south pretty quickly and could well cause water quality to go in the wrong direction. Water changes of 30% once per week can also introduce instability to the water and have a negative effect on fish and filters.......

    Hi Larry, do you remember what the title of the stocking thread is on KoiShack? I tried searching but couldn't find it.

    I think your statement of diminishing returns is important in that stocking rate is not DIRECTLY proportional to pond volume. I used to think that if we have 10 30" koi in a 10,000 gal pond with two Nexus 300 for a turnover rate of once per hour that it would be okay to stock 20 30" koi in the same 10,000 gal pond with FOUR Nexus 300 for a turnover rate of TWICE per hour. But I guess that this is not the case.

    I do like the "happy medium" concept though because then for a given 10,000 pond you can at least stock 18 koi, which for me would be very ideal. Not trying to cheat the system, but to explore stocking options that have been proven to work.

    Just to share and I hope that I will not offend anyone, but David Soon stocked 25 extremely high quality gosanke in his new 40 ton pond 2'9" deep pond. If my calculation is right, this equates to about 420 US gal per koi. His TOR is twice per hour and his filtration is like a nuclear plant!!!!!!

  10. #10
    Oyagoi Lam Nguyen's Avatar
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    Quote Originally Posted by schildkoi View Post
    Yeah, what Rob said!

    Almost everything can be explained through mathmatics in sme fashion or another. The problem here is that there are many variables and it would take a PhD mathmatician to even begin to attempt a formula that would come close to being accurate.

    On the flip side, there are a number of succesful design criterias that are known to work for given stocking densities and husbandry techniques. Sometimes it is simply easier to replicate successful applications verses attempting to understand all of the intracies in order to apply such to another set of design criteria only to find out that a variable was unaccounted for and thus leads to a less than optimal result.

    Steve
    Hi Steve, not trying to put you on the spot here, but could you please share with us some of the pond designs that have worked for high stocking densities?

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