What follows is almost completely based on the instructions written by Jerry in the Black Soldier Fly Blog.
1 x 25 litre lidded bucket with lid £9.99
1 x length 40mm PVC pipe (black is cheaper) (1.5m) £1.64
1 x length 22mm overflow pipe £1.99
1 x ‘T’ joiner £0.99
1 x straight coupler £1.49
2 x 22mm 90deg elbow £1.20
1 x 35cm plant pot saucer £3.49
1 x length 22mm clear Plastic Pipe £3.98
3 x small plastic flower pots (70mm high) £0.18
1 x piece weed suppressing membrane .. .. ..
1 x Water butt tap £3.37
PVC cement, silicone sealant, PVA glue .. .. ..
Taking my lead from the BSF blog instructions, but with a couple of my own variations, I purchased a 25 litre lidded bucket from Kernow Grow and Brew in Penryn, plumbing bits from Wickes (following the cheapest route), plant pot saucer from The Range, clear plastic tube from Chacewater Aquatics, and the water butt tap from eBay. Everything else comes from my own personal junkyard!
I first cut the 40mm pipe, two pieces for the top of the vent and a short piece to go through the lid, then I used a hole saw on the lid. The straight coupler goes on the underside of the lid, just to secure the vent in the hole. All this is assembled with PVC cement, and that is the lid complete.
Next, I used a small hack saw to trim the saucer to size, so that it sits 70mm from the bottom of the bucket and tight to the sides, with the edge turning upwards to contain soldier grubs and compost away from the edge and for better drainage.
I drilled several holes in the saucer (and caused two or three cracks to appear) and cut a piece of membrane to size. The membrane is glued to the saucer with a number of blobs of PVA glue – I’m not sure how effective this will be – I may have to rethink the filter!
The three flower pots are held in place, upside down at the bottom of the bucket, with silicone, to support the filter.
For the exit point for the mature grubs I drilled a hole for the 90deg elbow, which needed to be 25mm and just under the lip at the top of the bucket. Unfortunately I found drilling a clean hole in the soft plastic of the bucket difficult, so this is a bit of a dog’s dinner. It is held in place with silicone, but not well – but this doesn’t matter as the joint doesn’t need to be watertight. I have connected the other elbow to it outside the bucket with 45mm of 22mm pipe (I had to buy 2 metres!). A second length of the 22mm pipe comes down from the elbow, and will lead into a container for the mature bugs to become flies.
The ventilation slots were cut, as suggested by Jerry, by drilling a hole at each end of each slot, and cutting through with a hacksaw blade. The water butt tap required a 25mm hole to be drilled near the bottom of the bucket, and I fixed the tap on its side, to allow the hole to be as low as possible. Of course I could put the bucket on a stand of some kind and set the tap properly – but it really doesn’t matter!
I await the arrival of my soldier fly larvae (I have ordered 100 small ones) which cost £5.15 including postage.
Wish me luck!