What Black Soldier Fly Larvae Can and Cannot Eat

The appeal of a black soldier fly bin is its range. It handles material that defeats every other home composting method. But "eats anything" is not quite right, and the exceptions are where bins fail.

What They Handle Well

• Fruit and vegetable waste — the staple
• Meat and fish scraps — the thing a worm bin cannot do
• Dairy — also off-limits for worms
• Cooked food, including grains and leftovers
• Spent brewery grain and coffee grounds — both well-used commercially
• Manure — a major industrial application

What They Handle Badly or Not at All

• Woody and fibrous material — twigs, bark, cardboard. Larvae are not termites; they cannot break down lignin.
• Whole citrus in quantity — acidity and oils; small amounts are fine, a bin of it is not
• Bone and shell — the soft tissue goes, the hard structure stays
• Anything heavily salted, oiled or preserved
• Dry material — not a food problem but a moisture one; they need it damp

The Two Failure Modes

Too wet is the more common one. The substrate goes anaerobic, the smell turns genuinely bad, and larval activity drops. Add dry bulking material and improve drainage.

Too dry is the quieter failure. Feeding slows and larvae migrate early looking for better conditions — you get small prepupae and a poor yield.

The Rule That Covers Most of It

If it rots, they eat it. If it needs to be broken down by fungi over months, they do not.

And the substrate rule from every other page here still applies: what goes in determines what comes out. Larvae destined to be fed to an animal should be raised on material you would be comfortable naming. See how to start a bin.