Starting A Black Soldier Fly Bin

Leenie Wilcox
Aug 18, 2022
6 min read

When you move in to a new house, what is the first personal alteration you make so that it feels like home?

Apparently, I make a bucket to hold fly larvae.

Not very Pinterest-able I suppose, but these larvae are my first endeavor for a reason.

They’re called black soldier fly larva, or Hermetia Illucens, and they are expert eaters. The adult flies, however, are not expert eaters. Mostly because they don’t have mouths, or a way to excrete waste for that matter [1, Ch 1]. While they can fly, they cannot bite, don’t carry disease, and their larvae convert waste food into compost and highly nutritious body mass [1, Ch 1].

When a black soldier fly larva has reached maturity, it tries to crawl up and out of the rotting waste that was once its soul source of sustenance [1, “Ch 1]. This natural instinct makes harvesting larva at their largest and juiciest very easy.

So my 500 new pets will make my trash a little lighter, my composting a little faster, and produce a free, nutritious food for chickens, fish, and other livestock.

My setup is fairly simple; a basic tub with draining capabilities, a ramp for harvesting, and a light screen top where I place some cuts of cardboard. A detailed description of how I built my larva farm is below.

If it weren’t for the mosquitoes which have plagued the property since before I arrived, I could watch them eating scraps for hours. It’s strangely akin to watching a fire or a fish tank.

I also created an Excel spreadsheet to keep track of the larvae’s value. Of course, the “science” I am conducting with this data collection is informal enough to make any scientist’s stomach turn. The point of my record keeping, however, is only for a vague estimation of input to output ratios, so be still my heart, it will all be okay.

Essentially, I timestamp each day with the weight of food scraps I put into the bin, the weight of larvae harvested, and the estimated value of one pound of larvae. Then I run a macro which puts all the data in their proper places, calculates the day’s harvest value, and adds that value to the total running sum. The template and code are below if you want to do a similar data sheet.

At the time of this post, my flies have been in their new home for some time and the first generation of larvae have become beautiful adults. During this establishing phase, I didn’t harvest any flies to be assured of a strong second generation. This was, perhaps, overly cautious. I likely could have harvested many larvae without fear of eliminating future generations, since one adult female black soldier fly will lay approximately 500 eggs [1, Ch 1].

After seeing my first adult flies, I placed the harvesting ramp in the bin and began looking forward to collecting larvae.

Setup

The construction of a black soldier fly larvae farm does not need to be complicated or expensive. I am fortunate and have a shed that locks, so rain, raccoons, and unsightly plastics ruining an aesthetic garden were not concerns.

Materials

My suggestion is to get crafty in order to save money. Not everything needs to be beautiful. First make it functional. I made my bin out of scraps, trash, and only bought what could not be found. Below are my materials and the price for which I obtained them.

Cinder Blocks : Free
Weed Barrier : Free
Gravel/Rock : Free
Equine Heavy Duty Tub 40 Gal (Tractor Supply Co) : 52.99
Ball Valve Poly 3/4 “ 60410 (Tractor Supply Co) : 18.99
3/4 “ PP Bulkhead Fitting (Tractor Supply Co) : 11.99
Nipple Male TPT 3/4 “ (Tractor Supply Co) : 2.49
Live Black Soldier Fly Larvae 1/2 inch, medium, 500 x1 (The Critter Depot) : 21.00
5 Gallon Buckets : Free
5 Gallon Bucket Spin Top Lids (two from Lowe’s) : 18.99
Luggage Scale (Walmart) : 8.15
Wood For Ramp : Free
Screen Lid On A Wooden Frame : Free
Cardboard : Free

Total : 134.60

Building Process

After drilling a hole in one side of the trough, I screwed in a 3/4 “ pipe fitting, followed by a converter nipple, and finished off with a ball valve (a twisting faucet top). I placed the trough on two rows of cinder blocks (not displayed in video). The reason for the second layer is two fold; one, it brought the bin closer to to the light from the window which is essential for egg-laying. Two, because a 5 gallon bucket can easily fit under the spigot when the bin is placed on two layers of cinderblock.

Next, I filled the bottom evenly with gravel until it was just above the level of the drain pipe. This helps to prevent clogging the spigot and reduces the danger of larvae drowning.

Finally, I cut some weed liner to snuggly fit on top of the gravel. This again is a preventative measure for spigot clogging.

This is when I put the larvae in the bin and began feeding them.

The harvesting ramp can really be any design you choose. I took some scrap wood, sawed it into a triangle and screwed some shoe moulding scraps to the sides for guard rails. The whole thing was very much eyeballed, and I’m afraid if I say much more the carpenters out there will groan. Basically, anything angled, with protective sides, and enough frictional grip will suffice.

The final step in the building process was a lid. I could have left it without one, but I have more plans for the shed that the larva farm is sheltered in, so a lid was necessary. Since my flies are already covered by a roof protecting from rain and more severe weather, and since adult soldier flies prefer light in their selected egg-laying sites, my main incentive in a lid was to keep large creatures out. So I salvaged an old screen fitted to a frame that had once served as a tool to sift rocks out of soil. I placed this loosely on the top of the bin, put pieces of cardboard on top for egg-laying fodder, and dubbed the larva farm complete.

Excel

Here is a picture of my sheet. There is nothing special about the colors, borders, or data that is currently in the columns. You can customize these features however you like, only keep the locations of the cells identical (unless you plan to edit the visual basic code).

In cells J4, J5, and J6, I type the respective labeled quantities on a given day. Then I click the “Input Data” button, to which I have assigned the macro whose code is below. The data from the input cells then populate the proper columns, additional data are filled into non-input columns, and the input cells J4 and J5 are cleared. J6 remains until it is updated.

Visual Basic Code:

Sub BSFData()

‘ Collects Input Data, Places it at the end of the list, updates the graphs which

‘ depict the amount of input to output. Updates the total amount of “money” made

‘ (total value of converted trash into bsf, not including compost) and empties the input cells

TodayAmountFed = Range(“J4”).Value

TodayAmountHarvested = Range(“J5”).Value

EstimatedValuePerLb = Range(“J6”).Value

TodayDate = Date

‘calculate the value of today’s harvest

TodayValue = TodayAmountHarvested * EstimatedValuePerLb

Application.Goto Reference:=Worksheets(“Data”).Range(“B4”)

CurrentDay = False

‘find the next available slot to fill in today’s information, and set the date of today

Do Until CurrentDay = True

If IsEmpty(ActiveCell) Then

CurrentDay = True

ActiveCell.Value = TodayDate

Else

ActiveCell.Offset(1, 0).Select

End If

Loop

‘ Input the values for the day

ActiveCell.Offset(0, 1).Select

ActiveCell.Value = TodayAmountFed

ActiveCell.Offset(0, 1).Select

ActiveCell.Value = TodayAmountHarvested

ActiveCell.Offset(0, 1).Select

ActiveCell.Value = EstimatedValuePerLb

ActiveCell.Offset(0, 1).Select

ActiveCell.Value = TodayValue

‘Finally, clear out the input values of fed and harvested. I choose to leave the estimated

‘value per pound so that I only have to update it when I feel like it has changed.

Range(“J4”).ClearContents

Range(“J5”).ClearContents

End Sub

* A note to anyone uncomfortable with coding or Excel but who secretly wants to learn: Don’t be afraid. Anyone can do it. There are a lot of resources on YouTube, Google, and if I get requests I can do a few tutorials here on my blog. I consider myself a decently experienced coder, but I still spend a lot of time being confused, looking things up, and juggling obnoxious syntax errors.