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, 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.
>> Link YouTube: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 places 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, nearly-gone-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, 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 or makes it hard to breathe. 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 in which the heat makes the water droplets evaporate fast.
What I find the Bsf eat is:
- Fruits: banana, mango, papaya, dragon fruit
- Veggies: gourd, some microgreen leaves, cucumber, yam
- Meat & Skin: chicken, fish, duck
- Mushroom: paddy straw, oyster mushroom, shiitake
- Cooked rice
Currently, I'm experimenting feeding them with duckweed & bokashi compost.
From feeding them a bit of this and that foods, what I also find is the larvae eat soft foods (banana, steamed rice) faster than harder foods (cassava, yam). They also move their bodies more vigorously when eating softer foods.
Because of this, some growers intentionally use hard foods to lengthen/stretch the eating time, so it takes longer for the larvae to finish up their foods. This helps when there's a food shortage and also prevent the larvae from crawling out and pupate pre-maturely.
The problem of chicken bones & mango core (pulp):
If you feed the larvae with chicken bones, especially the thighs with a long tube, be careful because several larvae can squeeze inside to suck the bone marrow and get stuck in there. It looks funny, but oh poor little larvae.
I've seen several (more than 10) larvae stuck their bodies in one small tube-like bone. Poor them, they got in when they were younger & smaller but when they are bigger they can't get out.
Similar with mango core, there's lots of hairs/fiber on the core especially when it's more dry after several days, making it slightly difficult for larvae to move around. As an analogy, it's like a jungle with lots of roots, hairs, branches and strings.
So as a short conclusion, either smash the bones or give them more open-surface foods for easy moving around.
What the Larvae Don't Really Like To Eat
>> Link YouTube:BSF Larvae vs. Hamburger
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' or most costly part 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: breaks starch into simple sugars
- lipase: breaks down lipids/fats
- protease: breaks down proteins
We see there is little enzyme to break down lignin or cellulose in the BSF stomach. Although they have some gut bacteria that can help chop up the cellulose, the type of bacteria present may also 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.
From my experience, what I also find the larvae don't consume well is:
- Banana peels
- Shrimp shells
- Quail egg shells
- Unsmashed chicken bones (they do eat the chicken meat scraps on it though)
- Tomato skin
- Mango core (when they are really hungry they'll be less picky and chew on the fiber)
- Coco coir
- Salmon fin
So the idea for this is: What you feed them but they don't like eating, you'll end up collecting the undigested foods as part of their frass (larvae poop + undigested foods + skins). There's also good use for it around the farms and gardens.
To get some ideas on what to do with this leftover BSF frass, here is a post about this 'What to Do With BSF Frass (Some Ideas)': https://zenyrgarden.com/what-to-do-with-black-soldier-fly-frass/
The next question many growers have is:
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 okay 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 nutritionally. 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:
On the topic of manure, I had a chance to ask a master grower this question:
Can BSF Larvae Eat Worm Castings?
From his experience, worm castings may not contain the most good nutritionally for the BSF as the worms have fully decomposed most of the foods. He usually advises fellow farmers to use a balanced diet of fruits and veggies with some starch mixed in for energy. This helps the larvae grow the most optimally in strength and size.
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. For some foods when you turn too much, they may turn runny.
When turning the foods, you could use a windshield wiper or a trowel. Move gently so it doesn't accidentally cut the larvae.
How Much Do BSF Larvae Eat
BSF larvae can eat up to 5-10 times 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 5- to 7-days-old larvae, their consumption rate can be about:
- 1.3 kilos of 7-day-old larvae - 50 kilos of soybean waste for 3-4 days
Or about 12.5 kilos of soybean waste per day for 1.3 kilos larvae (about 1:10 ratio)
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. They won't die with less food, but just shrink smaller in size and weight, pulling you back to square one and delaying fly growth emergence.
Summary: What Food for Your Larvae
If You Want to Mix a Feed Without an Extremely Unpleasant Smell, Try:
- Oats/barley/bran/brewery grains
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 nut 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.
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. Trust me, oh the smell, you wouldn't enjoy it yourself or would want to share with others as carried through the wind. These more plant-based foods are suitable 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.
In stories told by other farmers, 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
- 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.
- Enzymes in BSF larvae digestive tract: https://www.sciencedirect.com/science/article/abs/pii/S1226861510001160
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