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Getting Better Growth

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  • Getting Better Growth

    Hello All

    I am needing some advice on improving the growth rate in my main pond. My current specs are as follows:

    25000 litres 6mx3.5mx1.2m deep
    I have two x .75kw pool pumps one pump runs through a veggie filter, and the other runs through approx 20m of 110mm pipe with filled with bio-balls.

    I have four filter chambers that both pumps pull water from. each chamber is 70cm by 70cm by 1.2m deep and collectively they are filled with 12000 plastic hair-curlers and bio-balls with significant air pumping through it

    I have a central bottom drain that has an air diffuser on top which has an airpump linked to it doing about 350 litres a min - it pushes bubbles almost 15-20cm above the surface of the pond. I have a second pump 160l per hour that pushes air down a pipe on the side of the pond. with 6 holes releasing a stroing curtain of bubbles.

    I reckon that at best I am getting about 2cm a month on some fish and about 1.5cm on others. At the moment I have

    1x 60 cm
    4x 55cm
    20x 25-35cm

    I am feed ing Aqua Master Hi Growth mixed with saki-hikario growth.

    What am I missing? Is my stocking density too high? Will a bakki shower help?I know I have tons of bio media. I have fairly good qaulity fish and bloodlines are not the issue.

    Can some of the experts offer some sound advice please

  • #2


    One BD can not service a 16x3.5m floor. The pond needs one bottom drain with air dome in each logical half of the pond...not one for the whole pond.

    Also pond depth of 1.2m too shallow to allow for vertical exercise of muscles and swim bladder. Remember koi are riverine carp. They need depth and current.

    Have not seen skimmer mentioned?

    double the depth and create some serious currents (koi are riverine fish)
    one BD with air dome for each half of the floor
    two skimmers (on each corner of one short wall) feeding a bakkin shower that returns water on the opposite short wall
    return water from BD filters via TRPs to help create currents
    no more than 1 koi for each 2000 liters regardless of current size of the koi...remember that they will grow large if their genetics, environment, and nutrition allow it
    Koi keeping is not a belief system; it is applied science with a touch of artistry.


    • #3

      OK so
      "Build a new pond" has been clearly covered.
      How MUCH are you feeding?
      Not how much in terms of lbs or ounces...or grams, but how much in terms of frequency and how do the koi react to the food through the feeding ANd how much remains at the surface for how long.
      One thing I can tell you right now. in that shallow a pond I'd suggest you feed them sinking food. I consistently hear that deeper water is a requirement for bigger fish. And I tend to believe there is a grain of truth to it. A pond should be twice as deep (at least) as the fish that are going to be grown out in it.


      • #4

        King Kong posted up a link to this you need to watch.

        YouTube - V59 13/3/10 Visiting David Soon's 4 Ponds

        Your pond shares two thing in common with David's.
        1 You both have Koi.
        2 You both have Shallow Ponds.

        After that, you have nothing in common.
        If you want to have good/excellent results with a shallow pond you need to follow his example on filtration, feeding, currents, etc... With your current setup you are completely screwed.
        If you want to go deeper (as MCA suggested) you still need to completely re-vamp your filtration and throw out the veggie bog altogether. They look fine on paper but they will never give you the kind of performance you need to achieve your goals.
        Larry Iles


        • #5


          Luke - I feed about 8x per day with an autofeeder - rough every hour and a half. This amounts to I would estimate around 500g per day - this fish eat eagerly for the first minute and then slow down, but all food is eaten within about 3minutes,



          • #6

            so you actually have a bog filter, and you have "good bloodlines" by your own assessment?
            Bubba that don't match up...
            the only person that has good growth and good fish and good water quality and uses a bog filter is Brett..and his bog is a few acres in size....
            So now we gotta get some real numbers and look at what you got for fish and where you got em, and when.
            And then we are gonna need real numbers instead of your announcement that the water parameters are good.

            But to continue along the not enough food idea...feed em every hour and make sure that a pellet or two is left ..the fish may over eat in the beginning but pretty soon they'll become more laid back and only eat what they need...
            of course your filter has to be able to handle the extra food/effluent?


            • #7

              Quinton: You have given a nice overview of your pond, but not the information needed to identify what may be limiting growth. [BTW, 2.0 cm per month could seem fine in a cold climate.] You seem to feeding plenty of food, so the remaining factors are temperature and water quality. Given your location, I expect you have pond temperatures in optimal growth range for 7 months of the year, which should be fine. So, that leaves water quality. Questions: What is the nitrate reading for the pond? What is the nitrate reading for your source water? How much water is changed out daily/weekly? [I presume there is no detectable ammonia or nitrite. If there is, we need to focus on your filtration and filter maintenance before going further.]

              In regard to stocking, you will need to limit yourself to 6-8 koi to obtain large size. So, start thinking about which of those tosai will need to move on.


              • #8

                Pond Readings

                Hi Luke/Mike

                Just taken readings and they are as follows:
                PH 6.5
                Ammonia 0
                Nitrite 0.2
                Nitrate 5
                GH 80
                KH 10
                Alkalinity 20

                The last two seem to be a problem?

                Luke, just to clarify the veggi filter is not my main filter and is just there for show really. I have 4 chambers 70x70x1.2m deep that are filled with platic curlers - 12000 in total that act as mechanical and biological filtration. I literally agitate each chamber shaing off any dirt and flush to waste - takes 15min. I do this weekly and drain about 10% per week.
                I also have significant air hoing into the pond - the equbalent of around 450l/min going into the pond - most to a diffuser head on the bottom drain. this produces seriuous air and current - it lifts bubble burst above the surface by about 15cm. very little is left on the floor despite only one drain. I also have a large skimmer on one wall.

                Luke on my fish

                local maruten sanke

                Sakai Tosai - tomahawk

                Local sanke

                What can I do to adjust the alkalinity and KH? Could this slow the growth


                • #9

                  Can you provide some numbers on your source water? Your kh is painfully low, especially with only 10% weekly water changes to replenish your buffering capacity. The large number of tosai you have (and they WANT to grow), you are running a razors edge from ph crash issues. That crash potential will grow exponentially as those younger fish grow.

                  A continual source of kh buffering, either from more frequent water changes and/or another source of kh ie. oyster shells, corals, etc... in your filtration would be in order along with thinning your numbers down.
                  Larry Iles


                  • #10


                    Hey Pappabear - I do have coral in the pond- clearly not enough though. how many kg's would i need?


                    • #11

                      Source water


                      My water locally is very good - low chlorine, and generally most local koi keepers fill straight from the mains without even adding chemicals,

                      ph - just over 7
                      kh - matches my current reading of 10



                      • #12


                        I agree with most of what has been pointed out. I'd like to say again, that your pH is dangerously low, and your water doesn't appear to have much for a buffering capacity which puts you in the danger zone for a bad pH crash.

                        Personally I feel your overstocked big time. I would pick 6-8 of your koi regardless of their current size and re-home the rest. You're getting a detectable nitrite reading so IMO your already sliding down a slope that's only getting steeper as the koi mature.

                        I'm sure your DO is quite high by virtue of such a large surface area and a low volume of water.

                        Do you find the bottom stays clean? And by clean, no collection of mulm and any fresh waste migrates to filtration quite quickly?

                        The food you're feeding seems fine.

                        As to oyster shells, or coral... someone else might be able to give you an exact weight, but the easiest way.... keep putting it in until your gH and kH get a little safer, then you've got enough!

                        Best wishes,



                        • #13

                          There is detectable nitrite, so there is a filtration/stocking problem. The low KH is a fundamental problem. It needs to be addressed in a manner that results in stable water conditions. The usual advice is to use oyster shell or coral in a shower filter. Another approach would be to have a constant in-flow of fresh water.

                          I consider a 10% weekly water change inadequate for maximizing koi. You will find those at the top of the pyramid of koikeepers often have a 10% per day continuous in-flow of fresh water. Personally, I cannot use that approach. So, I change 35-40% weekly.

                          If there is any chlorine in the source water, you need to use a dechlorinator, even if not much is needed. The cleaner the pond environment, the more dangerous the chlorine. Long term exposure is not a good thing.


                          • #14

                            Quinton: I've bumped up a thread on water changes. Wade through it and think about it.


                            • #15

                              Thanks, much appreciated - am am going to thin out my fish a little, introduce some coral etc in a hurry, and get a bakki shower asap. will kepp you updated on the progress. What would a good growth rate be at different ages? toasai? nisai? My tempreture here in Cape Town is around 22degrees at the moment and I have tempretures beteewn 20 and 26 for about 8 months of the year, with tempreture never really dropping below 10deg.


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