If you keep reptiles, amphibians, or wild birds, black soldier fly larvae (BSFL) are one of the most useful feeders you can have on hand. They're nutritious, low-maintenance, and unlike a lot of feeder insects, they don't need much from you to stay in good shape. Here's what they are, why they're worth feeding, and exactly how to keep them alive and healthy once they arrive.
What are black soldier fly larvae?
Black soldier fly larvae are the larval stage of the black soldier fly, a non-pest insect that doesn't bite and isn't a disease carrier. As a feeder, they're prized for one thing above all: calcium. BSFL are naturally very high in calcium, with an excellent calcium-to-phosphorus ratio, which is exactly the balance most reptiles and amphibians need for healthy bones and growth.
That high calcium content is what sets them apart from staples like mealworms or crickets. It also makes them genuinely low-effort to feed, which we'll come back to.
Why they're such a good feeder
The biggest advantage is that you don't need to gut-load or dust them. Because BSFL are already rich in calcium, they deliver real nutritional value straight from the tub. With many other feeders you have to gut-load them with nutritious food or dust them with a calcium supplement before feeding, an extra step, extra cost, and one more thing to remember. BSFL skip all of that.
They're a great everyday feeder for:
- Reptiles like bearded dragons, leopard geckos, and other lizards
- Amphibians such as frogs and toads
- Wild and pet birds
They suit animals that appreciate a soft-bodied, calcium-rich insect as part of a varied diet.
What size should I feed?
Match the feeder to your animal. As a rough guide, a feeder insect should be no wider than the space between your pet's eyes. NutriGrubs BSFL come in three sizes:
- Small — approximately 1/4″
- Medium — approximately 1/2″
- Large — approximately 3/4″
Smaller animals and juveniles do well on Small; larger lizards can take Medium or Large.
How to keep them alive and fresh
This is where BSFL really shine, they need almost nothing from you.
At room temperature, out of direct sunlight, they need no food or water through their shelf life. Keep them in the ventilated tub they arrive in, leave it on a shelf, and they'll be fine. That's genuinely all most people need to do.
To slow their growth and extend shelf life, store them cooler, in a wine fridge or similar at 10 to 12°C. This slows them down so they last longer before maturing.
In those cooler, optimal conditions, you can expect roughly the following shelf life (we err on the side of caution):
- Large — 7 to 10 days
- Medium — 10 to 14 days
- Small — 14 days or more
A good rule of thumb: never buy more than you can realistically feed off within these windows. Order to your feeding schedule and you'll always be using them fresh.
Do not use a normal household fridge. A standard fridge runs around 4°C, which is too cold for BSFL and will harm them. A wine fridge or a cool basement is ideal; the regular fridge is not.
Before feeding, let them warm back up to room temperature. A cold feeder is sluggish and less appealing, letting them warm up brings back the wiggle that triggers a feeding response.
Feed off the dark ones first. You can't control exactly when a larva decides to pupate and turn into a fly. When you notice one turning a dark coffee-brown colour, that's the sign it's getting ready to mature, so feed those to your pets first. If you keep animals that enjoy the flies themselves, like chameleons, you can deliberately let a few mature for them.
Feeding them off
When you're ready to feed, dust or shake off the substrate they come in, then place them in a feeding dish with steep, smooth sides. They don't like light, so if they can climb out they'll escape the dish and burrow down into your enclosure's substrate where your pet can't get at them. A steep-sided dish keeps them contained and in view until they're eaten.
A quick word on freshness
Feeders are only as good as they are fresh. At NutriGrubs we breed our own black soldier fly larvae right here in Calgary, so what you get is fresh, quality-checked, and hasn't spent weeks in transit before it reaches you. Fresher larvae are more active, more nutritious, and more likely to get eaten.
The short version
Black soldier fly larvae are a calcium-rich, low-maintenance staple feeder that don't need gut-loading or dusting. Keep them at room temperature out of direct sun for easy short-term storage, or at 10 to 12°C (never a household fridge) to make them last longer, and always warm them to room temperature before feeding. For most keepers, they're about as easy as a live feeder gets.
Ready to try them? Shop our fresh, Calgary-raised black soldier fly larvae in Small, Medium, and Large.
