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Planning a new system!! Maths doesn't stack up?

Discussion in 'New Aquaponics systems - DIY' started by ReyZr67, Oct 31, 2017.

  1. ReyZr67

    ReyZr67 New Member

    Joined:
    Sep 15, 2015
    Messages:
    23
    Country:
    Australia
    State:
    WA
    City:
    Perth
    Hi all. Apologies in advance for the long post, it has been a while...
    Finally we are facing the inevitable upgrade after 3 years of my 4000LT system. This is the old system being migrated from the side of the house to the backyard. 6 x IBC growbeds (actually only 5), 15 x 20LT dutch buckets (fruit trees), 1500LT submerged surge tank, and 2 x 1000LT IBC fishtanks in the garage (not on this pic). Stocked with 30 x silver perch and 5 x comets (used for cycling 3 years ago ):
    2017-10-31 (1).png

    Why the move?
    1 - Just cannot keep nitrates down!! Always off the chart, as soon as 3 weeks after a COMPLETE water change. I feel I am overstocked, but anyway...
    2 - Poor initial design of the beds up against the fence. Makes it difficult to maintain/harvest from one side only. This is the main reason.
    3 - Not getting min 6 hours of full sun due to sun's path v AP orientation. In the picture above, the sun travels basically from left to right along the bottom of the pic, so only after about 10am does it fully clear the back fence, and disappears behind the house again around 2. Full day sun in the back garden however.

    The new plan?
    8 x IBC growbeds, same 1500LT submerged sump (bottom of pic), no dutch buckets (just too finicky with AP), 6000LT fishpond stocked with Koi (top of pic).

    2017-10-31.jpg

    Current questions:
    Apparently I need more understanding of nitrate control - as above. First to address stocking.
    1 - Plan is to only stock around 10-15 koi, based on previous experience with skyrocketing nitrates (and yes, only feeding a handful of skretting every second day, <10% growbed area used for "fruiting" plants (tommys, capsicums, etc) with the rest being leafy greens, but still soaring!). Assuming 15 koi stocked, is 9m2 enough growbed area? Because a "rule" apparently states 0.5kg fish/m2 growbed area, which means only 4.5kg fish - or 1 adult koi???? This is my biggest conundrum!!!
    2 - Fishtank area is obviously not a problem as the "rule" there seems to be 0.5kg fish / 25LT of fish tank water, which means in 6000LT I can stock 120kg of fish yeah? However, another "rule" states 1 fish/45LT, which means I can stock 133 fish, which in adult form would be way over a kilo each? Either way though, I obviously have woefully little growbed area for that kind of stocking - just happy to give them big living area.
    2 - Another alternative would be to double the growbed area to 18m2 - easy enough to move the row over a meter or so and add another with a 600mm gap between rows I guess...

    So, in a nutshell: how many koi can I raise in this system, and should I invest in the time / energy / finances to double the growbed area - in your collectively well educated and experienced opinions?!?

    Cheers all
     
  2. Murray

    Murray Site Admin Staff Member

    Joined:
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    Queensland
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    Nice plan.
    In the long run it is not about how many fish or how big they are. It is about how much fish feed goes into the system. So, working back from that a low point of feeding that has been shown to work well is 10g per sqm of plant growing area. Have enough fish to eat that every day and you will be close to balance. That is assuming you have the grow beds planted to density.
     
  3. ReyZr67

    ReyZr67 New Member

    Joined:
    Sep 15, 2015
    Messages:
    23
    Country:
    Australia
    State:
    WA
    City:
    Perth
    Thanks Murray.
    I will make some work of the 10g/m2 over the next while with the existing system and see what happens. Appreciate the advice mate
     

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