We had a very interesting week at the commercial site. We have now finished 50% of the growbeds, filled them with gravel and planted some test plants. A summary of the system as it stands now may be in order.
There are two halves of the greenhouse which I am calling A and B. We have just completed the growbeds in section A and they are numbered A1 through to A12. The other side will be B1 to B12.
There are 4 fish ponds of 7800L each. They are P1, P2, P3 and P4. All the ponds are full of water.
P1 and P2 have no fish in them.
P3 has 16 very large Koi fish which are our test fish and will come out once the system is cycling. I’d estimate their biomass at 64Kg ie they weigh 4Kg each.
P4 has about 120 Tilapia fingerlings and some mosquito fish. They will also be moved to the dam when the system is fully cycled and the new fingerlings are introduced.
Then we have the 5000L sump which I will refer to as S. All water starts and ends in the sump.
Pond P1 flows by gravity to irrigate growbeds A1 to A6.
Pond P2 to A7 to A12.
Pond P3 to B7 to B12.
Pond P4 to B1 to B6.
There are two pumps, lets call them U1 and U2. They are on 1 hour on and 2 hour off cycles.
U1 pumps water from the sump to ponds P1 and P4, thus irrigating growbeds A1 to A6 and B1 to B6.
U1 pumps water from the sump to ponds P2 abd P3, thus irrigating growbeds A7 to A12 and B7 to B12.
I battled a bit to get sufficient flow to my grow beds because my drains at the bottom of my tanks are 80mm, it then flows to the growbeds with 50mm pipes and then reduces again to 20mm pipe for the spraybars. I overcome this by splitting the flow in 3 directions using 50mm pipes and THEN reducing to 20mm at the last minute. This provides enough pressure to the spraybars now.
We planted some test plants, strawberries, lettuce, rocket, chillis, watercress, mint and then various seeds directly into the gravel. We are going to try mushrooms in hessian sacks under the griowbeds. We will probably have to shade them a bit.
As far as heating the water, I have decided to rely on a very low-tech method. We are digging a 25m trench about 500mm wide and 1m deep along the one length of the greenhouse. I am running 40mm black pipe up and down this trench from my bypass line. We are filling this trench with sawdust. Water and dew will flow down the greenhouse and keep this trench damp. The composting of this sawdust (of which we have an unlimited supply) will heat the water up. We can control this heat by using a valve inside the greenhouse to regulate how much of this heated water goes into our system.
I have also introduced nitrifying bacteria from my home system directly into the completed growbeds. This can save up to 8 weeks waiting for the bacteria to establish itself naturally.
Some images below;
Half of the growbeds are now completed.
All of the water begins and ends in the sump (sorry about the blurry image).
Jaws, one of the monster Koi.
Some of the test plants introduced.
Enough for now.