Black soldier fly larvae eat just about anything organic-based or perishable. Decaying fish, meat, animals are good protein sources for the larvae. Kitchen scraps like carrots, banana peels, zucchini, spent barley, coffee grounds are also good nutrient sources. These guys do okay with fatty, oily, salty & even spicy food like Mexican or Chinese food.

Check out the baby larvae devouring a dead bird in less than a day.

If you're raising black soldier fly small-scale or large-scale, look for what's available in your local area for cheap or for free. Ask local food diners if they have any food waste they're willing to give. Scraps from veggie sellers in farmer's markets are also good. They often sell rotting fish, bad fruits for cheap. Some people also get the excess food from factories or household waste.

It's okay to feed them on a plant-only diet like greens, fruits, veggies, leaves, grass, beans, etc. Some people say on this diet the pupated flies may not be as strong to reproduce though. They may grow but quite slowly. If you're raising them to treat bio-waste, maybe this is enough. For reproduction, some extra protein from fish or meat may help. The downside to these high-protein stuff is the smell.

A good moisture content for the food is around 60-70%. People also shred the food so it's easier for the larvae to munch on. The moisture helps make the food softer & is where the babies get their water. It helps the larvae digest the food a bit easier & faster. Make sure it's not too wet because the excess water may drown them. Overly wet substrate makes it hard to collect the larvae poop afterwards, which could be used as a good fertilizer. This may not be a big issue if you live in a hot, dry area which makes the moisture evaporates fast.

What the larvae don't really like

From some growers' experience, the larvae don't really like the smell of onion. We guess then, they may not be into garlic or mustard. Because those stuff have a strong characteristic smell due to the sulfur content–like onion.

In fact, we can never force the flies to eat. If they don't like the food, they'll crawl somewhere else to find better food. You'll know immediately when you see it. Like the hamburger in the video above, the larvae don't even bother touching the meat patty (which is usually the 'meat' of a burger). Which makes many viewers question if it's even real meat or just fillers. If you want to test if the food is real or not, just throw it to the larvae. Nobody can fool these little guys.

Also, they don't seem to like fibrous (high-fiber) stuff with long chains of polysaccharides like cellulose or lignin. So coco fiber (coco coir), grass, wood chips, paper or cardboard may not be very attractive to the larvae. They can be good as bedding substrate to provide air flow though.

Explaining why the larvae may not like high-fiber foods from a more scientific point of view, the researchers found that the digestive tract of BSF contains 3 types of enzymes:

  • amylase: boosts up starch break-down into sugars
  • lipase: accelerates the breaking down of lipids/fats
  • protease: chops up proteins faster

We see little enzyme to break down lignin or cellulose in the BSF stomach. Although they have some gut bacteria to chop up the cellulose, the type of bacteria may depend on the food they take in. Lignin, the hard supporting tissue of many vascular plants (or the crunchy stuff we get when biting into a raw veggie), may not get digested very well. The microbes inside the larvae stomach might eat them though but the conversion may not be optimal.

The next question many growers have is:

How much do BSF larvae eat

BSF larvae can eat up to 5-10x their weight. You can feed them a ratio of 1:1, 1:5 or 1:10. Most people who raise BSF to get the eggs or their castings for resale would feed them with a lower ratio, for example, 1:1 or less to manage the food costs.

For those that are using BSF to treat bio-waste or garbage waste, they want a higher ratio of 1:5 or 1:10 for higher efficiency in less time. As they get the food waste from restaurants or local food stores, they don't have to worry much about the costs of the input.

In more concrete numbers you can see that:

About 100 kilos of food will be good to produce 18 kilos of larvae (without counting in their poop weight). In other words, 10 kilos of garbage daily is good enough to raise 1 kg of larvae for about 9-15 days. In numbers count, roughly, 600,000-800,000 larvae will eat about 1 lb (0.45 kg) of food. In space count, 40 kilos of fresh manure works for 1 square meter of larvae per day.

Let's say we go get some eggs to start our BSF colony:

They usually sell eggs by the grams. We'll buy 20 grams of eggs. Which is roughly 600,000 - 800,000 larvae as 1 egg on average weighs 25 microgram. In about 1-2 hours, they will eat up about 0.45 kilo (1 lb). So for one day we can prepare about 5-10 kilos of food for them.

They will consume like this for 9-15 days. When they've had enough & their bodies turn a bit darker like a salt-and-pepper mix, they'll automatically move themselves out. Some people soak the food in water to increase the volume & weight.

Grams of eggs Number of larvae Kilos of food per day
18 600,000-800,000 5-10

For 5- to 7-days-old larvae, their consumption rate can be about:

  • 1.3 kilos of larvae - 50 kilos of soybean pulp for 3-4 days
  • 1.3 kilos of larvae - 12.5 kilos of soybean meal per day (about 1:10 ratio)
okara-soybean-pulp.jpg
Soybean pulp (okara) to feed the larvae | Source

If the raising conditions are well enough, we can expect the following yield. Starting with 50 grams of eggs, after 2 weeks of feeding, you may end up with 200 kilos/440 lbs of larvae yield. They grow 5000x their initial body size.

Grams of eggs Kilos of larvae yield Pounds of larvae yield
18 72-75 158-165
40 166+ 365+
50 200 440

Summing it up, you can feed the larvae starting from a basic 1:1 ratio & adjust things depending on your needs and their re-actions.

Space Amount of egg Amount of larvae yield Amount of food
1m square 5 grams 20 kg 25 kg
10.7ft square 0.17 oz 44 lbs 55 lbs

If you start 5 grams (0.17 oz) of egg in a 1 meter square (10 ft square) space, in about 2 weeks you can end up with 20 kilos (44 lbs) of larvae. In other words, if you build a compost bin around 12-15 ft. square, then on average you can get a yield of 2-3 lbs of larvae a day. This can be used for fish food/pet food or whatever you see fit.

The amount of food for them, following a rough 1:1 ratio, over the 2-week period is about 25 kilos (55 lbs). Or about 2 kg/4lbs of food a day. A 50-lb bag of rolled oats which costs about $10-20 is enough to feed these guys for 15 days. It's pretty affordable & manageable, especially if you can find much cheaper food or free waste sources. You can then increase the food amount to 4-6kg/8-13 lbs. They won't die with less food, but just shrink smaller in size.

This is how we roughly calculate it:

Starting egg weight 15-day-old larvae weight (x5000) Larvae count Total kilos
25 microgram 125,000 microgram 600,000 75

The initial egg weight on average is 25 microgram per egg. After 2 weeks, they'll grow 5000 times bigger. So we multiply that by 5000, which gives 125,000 microgram or 0.125 grams per larvae. Then, we time that with the estimated number of larvae there is. If there's around 600,000 (~18 grams egg) in the starting colony, we get 600,000 larvae x 0.000125 gram per larvae = about 75 kilos of resulting larvae.

If you look at the size, you can see some significant growth:

Growth stage Weight (grams)
1 egg 0.000025
5 days old larvae 0.0012
15 days old larvae 0.125

When running through the numbers, please also add a margin of plus & minus depending on how many larvae survive after the eggs hatch. Also, remember these are not definitive set-in-stone numbers. Please correct us if we got something wrong. Be flexible & observe your local environment and their re-actions when you feed your babies.

As you can see, the ratio of amount of larvae to amount of daily food can be up to about 1:10. So you can imagine, if we have 4 tons of garbage to process daily, about 400 kilos of BSF larvae can help us with processing the organic waste & keep the cycle going in an efficient & sustainable manner. This is truly fascinating.

Also, it's good not to overfeed themselves from the start. The excess food may attract other stuff like houseflies or molds, which we do not want. You can start off with something easy like veggies, then move up to the more hardcore stuff like rotting meat.

When the larvae eat, they excrete out some pheromone. This smell will "shoo" away the other insects, wasps or house flies. That's what makes them so aggressive. Sometimes you'll hear their munching sounds as they chomp down on the food. They like a bit of privacy when eating, so shade is good.

If you feed them with something that is light colored, for example oats, soybean pulp or diluted porridge, after a few days the food may change to a darker color. This is when you know the larvae are munching on the food. Then, you know it's time to feed them again.

The larvae are really fast eaters. In 1-2 hours, they'll eat up everything. If you don't supply them in time, they'll move themselves out to some place to find food. Sometimes, they'll get noticeably skinny if you leave them hungry for a day.

Is manure good food for the larvae?

If the manure comes from a healthy animal, then it may be good. You can mix them with some water to create a paste for the larvae. Chicken manure, pig manure give good results. Chicken manure however may heat up the bin. If you can stand the smell, then using chicken manure is perfect for the larvae. Rabbit manure doesn't heat up as much and it is moist enough for the baby larvae. Larvae from 4 days old can eat this stuff with ease.

Some people find cow manure or goat dung not as effective. Because these animals eat mostly high-fibrous grasses, which the larvae don't find that appetizing. Growers find that the grubs grow slower & smaller on these foods. Also, inside the stomach of the BSF larvae are some strong acids & gut microbes, they can fight or deactivate some troubling viruses & bacteria like Salmonella.

See a quick comparison between BSF larvae fed on soybean waste vs cow dung here:

ten-days-old-larvae-cow-dung-soybean-meal-size-comparison.jpg

Should we turn the food?

It's okay to turn the food every now & then. This helps distribute the food more evenly to everyone in the house & helps the feeding area not get too hot. Don't turn it too much though. It might then be unnecessary because turning may slow down pupation & sometimes damage the larvae little bodies.  

Summary: Food for your larvae

If you want to mix a feed without an extremely unpleasant smell, try:

  • Oats/barley/bran/brewery grains
  • Fruits
  • Beans
  • Veggies

Basically, things that come from plants will give a slightly less unpleasant smell than that from an animal source (because of the high protein or nitrogen content).

In Indonesia, for example, rice bran is cheap–about $0.5-0.7 per kilo. So growers use that as food. The downside to rice bran is that it can create quite a hot feeding area, so remember to mix in some water, beer grains or cashew shells to space out & cool it down. In Cambodia, rice bran is expensive so they choose another food source. If you live in the US, a bag of 50 lbs rolled oats can be had for about $10-20. This is very affordable.

These less smelly foods are suitable if you live in a residential area & don't want to bother the neighbors, visitors or your loved ones with the smell. It's good if you're raising the BSF larvae indoors.

If you're okay with the smell & want to go into beast mode, try:

  • Chicken, pig, rabbit, cat poop
  • Decaying chicken, fish, shrimp
  • Dead BSF bodies

The larvae love meat! Any high-calorie, high-energy foodstuff will do. Make sure these come from good sources so your larvae won't be eating some sickly bits from the start. If you combine the BSF raising with chicken raising, you can utilize the chicken manure to feed the BSF larvae. Then, as they grow up you can feed the larvae again to the chickens. The BSF castings can then be fed to your worms.

These more smelly foods are great if you have a bigger raising space far away from residential houses which won't bother anyone around.

For smaller farms near people's houses, some farmers were forced to suspend or shut down their operations because of the reports to local officials of the foul smell. In this situation, pre-treat the feed with some enzymes or microbes (Lactobacillus or Trichoderma). The fermentation process can help get rid of the heavy smell while still retaining the nutrients in the food.

Also, try not to add too much water. This may drive away the oxygen & creates an anaerobic environment that causes the bad smell. After some fermenting, the food will now smell very light with a mild level of sourness that's bearable. This is easier to handle for the owners, the staff working there, the visitors to the farm & the animals living near by.

The advantage of these foods is that they boost up the larvae growth pretty fat & fast. From experience, these meat-fed guys are usually pretty badass. They are stronger & produce more eggs than the ones that are fed with plants mostly.

If you can't find fresh food sources, some people use processed food like:

  • Chicken feed
  • Biscuits/crackers
  • Shrimp feed

Overall, the key to choosing what the larvae eat is if you throw the food into the ground for 5000 years and it decays, then it's okay for the larvae to eat. If it's in the ground for 1 million year but still doesn't break down, then it's a no-no. Hope this brief post has given you some ideas for feeding your larvae. Good luck getting your black soldier fly colony started.

Sources:

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