With the tanks finished and some test Koi and Tilapia happily settled in, our focus now turns to grow beds. As mentioned a few weeks ago, we are trying big 500mm PVC pipes cut in half as grow beds. They will be in 3m lengths and I’ll close the ends with PVC sheet cut in half-moon shapes.
This is what the pipe looks like before cutting.
After cutting with an angle grinder.
And this is roughly what the grow bed will look like. We will now put ends on and build a stand to see how it will work. The two points that I am concerned about are firstly the fact that it will only give us a gravel depth of 250mm and also I am not sure how I am going to insert a drain, as the wall thickness of the pipe is about 10mm.
We are still waiting for the greenhouse to arrive and in the mean time have been giving thought to an algae pond. We are planning a 30m x 5m pond, 250mm deep. The bio-filters will backwash into this pond and we’ll also have runoff from the greenhouse into the algae pond.
I’d like to build something like this pond at Rhodes University.
We have graded a spot next to the slab in order to visualise it.
From this pond we are hoping to harvest about 1.5 tons of algae per week. which will provide us with valuable feed for the Tilapia as well as about 2000L of bio-diesel per annum. What we might want to do, is work out our annual diesel requirement and then work backwards to determine how big our ponds should be. With diesel at about R9/L this little by-product now become really feasible.
Enough for now.
P.S. I am very proud to announce that Synaptoman has been declared Runner Up in the Best Green Blog category of the SA Blog Awards. Many thanks to all of my readers who made the effort to vote. I really appreciate your support.