Here are some low-cost feedstock ideas for the black soldier fly larvae and their relative pros and cons.

#1. Coffee Grounds

The smell of coffee grounds can accidentally attract natural BSF in the area. So while feeding your larvae with this foodstuff, you may get a double benefit of attracting more BSF to the bin.

As coffee grounds are steamed and heated, they are comparatively more sterile than the other feedstocks. The moisture of the grounds is also nice for the grubs.

The downside to this, however, is that not everyone is a coffee drinker. If there's a coffee shop near your local area and they are having the grounds as waste, then it may be a good idea to ask for some supply from them.

As a next option, you can also feed the bsf with:

#2. Seasonal Fruits / Veggies

In some places, growers feed the BSF with seasonal fruits and veggies. Or basically whatever is available in an abundance for cheap. This could be cheap watermelons, left-over dragon fruits, papayas, pumpkins, sweet potatoes, the coffee berries, etc.

The plus side of this feedstock is that they don't smell too bad like some meaty stuff does. Also, they can be had for very cheap, which helps lower your feeding costs.

On the other side, not all fruits will be eaten by the larvae though. For example, they don't really enjoy the skin of citrus fruits. Because of the minty terpene oil in it. They do eat the flesh of citrus however.

No avocado seeds or rinds will ever get eaten. A grower though has the idea of grinding the avocado seeds into powder. Personally I have not tried this myself but I guess (I'm curious) if it could work. But the flesh of the avocado will be eaten fine.

Another thing to look out for is the potentially harmful pesticide or chemical residues in some fruits and veggies. For example, if you feed the larvae apples, you could first soak them in clean water for 20-30 minutes. Doing this will help remove some of the pesticides. Another thing is some fruits like watermelon can be quite watery.

#3. Animal Manure

The animal manure that work out well for BSF larvae are chicken manure and pig manure (if well treated). These are carnivorous animals that feed on more high-protein stuff.

Chicken manure, however, may heat up the growing area quite a bit. If you find this to be an issue, try rabbit poop. This stuff doesn't heat up the bin and has a nice moisture to it which the grubs like.

Cat litter is also okay for these little guys. It may be quite dry however. So before feeding, you could use a spray bottle to moisten it up.

Manure from grass-fed animals like cows, goats or horses may not be the best for the BSF. Because they are quite fibrous and contain the lignin or cellulose, they may not get digested well in the BSF intestines. The bio-conversion rate for the herbivore manure is around 6-10%. You may get 20% bio-conversion with higher-calorie feedstocks. And the obvious downside of using animal manure is the smell.

But again, the cost is cheap and the supply is abundant. The larvae grow quite strongly on these high-protein, high-calorie stuff compared to the fruity or veggie ones.

#4. Left-Over Foods

Oily, cooked foods are also fine for the BSF grubs. They tend to chew down on softer bones like fish or chicken bones faster than mammalian bones.

If you have some stale, expired oatmeal or chips, those will work as well. Remember to moisten them up before feeding to make it easier for the grubs to eat and convert.

Anything that's too woody or stemy like broccoli stems may be better for the worms, but not these bsf guys. In my experience, they don't seem to eat banana peels however.

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

What I also find the larvae don't eat very 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

For more information on what the bsf eat and don't eat, you could check out:

#5. Other Feed Ideas

  • Soybean waste
  • Duckweed
  • Pond mud

I didn't have a good experience growing duckweed as feed due to the space and light. It turned yellow. There was some algae developing in the water and some moving wiggly creatures (like the babies of mosquitoes). But I will try again.

Responses to Readers' Questions

My BSF larvae are dying while feeding on pig manure. What could be the issue?

--> Thanks for your question. In a reply via email, here are some notes again for consideration:

To start with the pig manure issue, in the feeding area you could check if there are darkened prepupae and cream larvae both developing. When the dark prepupae are about to crawl off, they will excrete out all the contents in their guts. This dark poop, from some growers' experience, if not collected, may affect the growing cream larvae. When the cream larvae meet this stuff, they may have a less appetite to eat or vomit out the food they've consumed. This could gradually make them shrink smaller in size and die off, and turn the feeding area quite mucky. If you notice this may be the case, you could filter out the dark prepupae poop in the corners where they gather. Some growers harvest the black ones out when the box is about half darkened. From an observation, early harvest when there are a few dark prepupae may cause other cream larvae to quit eating and follow. This could lead to premature crawl-offs.

Around your growing area, check if there's any scent of insect sprays, chemical sprays. The larvae are sensitive to these and some contact may turn them motionless. If it is not long after your larvae stop wiggling actively, you could try sprinkling a thin layer of yummy food (like chicken feed) to stimulate them to wake up again. They may wake up again but wiggle quite weakly at first. Some believe such food poisoning may turn the larvae inactive for some time, but good news is they may not be dead yet. In a similar case, a grower was able to re-activate the larvae from chicken mite sprayers in chicken manure with that simple tip.

Saving BSF larvae from food poisoning

Lastly, for a whole picture, you could check other aspects like temperature (make sure it's not too heated up especially in the center of the box), oxygen, and just enough feed for the BSF so fungi or other bacteria/pathogens won't grow on the pig manure.

I'm not sure if these pinpoint the problems and answer your questions. But I hope this helps.

I recently discovered that my bsf pupa disappeared after living them in a crate overnight. Do we have predators feeding on the pupa?

--> Thanks for your question again. Have you checked inside underneath the sawdust? The prepupae may bury themselves underneath to undergo metamorphism into flies. They need some darkness at this stage. When it's time and they are ready, they will automatically crawl up to the surface.

Please how good is brewer's spent grain as feedstock for BSF larva?

--> Thanks for your question. According to the farmers who have been using the brewery mash/waste, it is quite good for feeding the black soldier flies larvae. Some even share that in places people line up at the brewery just to get the waste. Take note that the amount you feed it will be proportional to the larvae weight, the more you feed the more weight and the less you feed the less weight. From what I've also heard, brewer's waste tends to have a heating property, so if you're raising a lot be sure to space out/stir or have proper cooling methods so the growing area does not get too hot (which could cause larvae escaping). I hope this helps!

I have access to a huge amount of mango peels, spent amngo pulp. Would it be suitable for the larvae ?

--> Hello, thanks for your question. From my own experience, the larvae do eat the mango pulp. I have not tried it with the mango peels so I cannot speak about this personally. But regarding the mango pulp, be a bit careful as the texture of the pulp gets a bit hairy (the mango fiber) as it gets chewed on and dries out over time. Because of the hairy surface, some smaller larvae may find it hard to move through (like a forest with a lot of vines), I've actually found some little ones (funnily) got stuck between the hairs. In any case, I'll ask in a group if mango peels are suitable for them. Until then, I hope this helps & See you again next time!

Hello again. Regarding the mango peels, yes they are suitable for the larvae. Remember to choose the ripened ones, as most ripened mango peels are full of water soluble nutrients and sugars, which are good for the larvae growth especially when mixed with other dryer byproduct materials like rice bran or pollad etc. I hope this helps. Thanks!

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