Discoid Roaches vs Black Soldier Fly Larvae: Choosing the Right Feeder
I've run a discoid roach colony for years and I keep black soldier fly larvae in the fridge as my "calcium insurance," so this is a comparison I live every week. Both are excellent feeders for a bearded dragon, and the honest answer to "which is right" is usually "both, for different jobs." But if you're choosing where to start, here's how I think about it.
Why the feeder choice matters
A bearded dragon's protein comes from insects, especially in the fast-growing juvenile months, and the feeder you pick shapes growth, weight, and bone health. Two factors do most of the work: the protein-to-fat balance and the calcium-to-phosphorus ratio. Past that, practical stuff (cost, sourcing, shelf life, whether you can breed them) decides what you'll actually stick with. Discoid roaches and black soldier fly larvae (BSFL, also sold as calci-worms or calcium worms) sit at interesting opposite ends of those trade-offs.
What discoid roaches are
Discoid roaches, Blaberus discoidalis, are a tropical, flightless roach from Central and South America. People often confuse them with dubia roaches (Blaptica dubia), but they're a different species. A few things make them a keeper favorite:
- Lean protein. Roughly 20–25% crude protein on a dry-matter basis with a relatively low fat content, so the protein they deliver is lean.
- Soft-bodied for a roach. Less chitin than a cricket, so they digest easily.
- No real odor when the bin is kept clean, unlike crickets.
- Can't climb smooth walls and can't fly. A smooth-sided tub contains them with no lid drama. (Some old guides claim roaches scale smooth glass, discoids don't.)
- Long-lived and easy to breed, so a colony pays for itself.
The trade-offs: they cost more upfront than crickets, they want a warm, fairly humid bin (85–95°F is the sweet spot), they're not stocked everywhere, and adults can be too big for a small juvenile dragon, so you size down to nymphs.
What black soldier fly larvae are
BSFL (Hermetia illucens) are the standout for calcium. This is the one feeder I'll genuinely call calcium-rich: their calcium-to-phosphorus ratio naturally meets or exceeds the ideal 2:1, which is rare and valuable, since nearly every other feeder is phosphorus-heavy and needs calcium dusting to compensate. They're soft, easy to swallow, low-fat relative to something like a waxworm, and require almost no care, you keep them cool and use them. Their downsides are real too: they're small, so an adult dragon needs a lot of them to feel fed, they're a single-use feeder you can't realistically breed at home, and they pupate fast if they get warm.
Protein and fat, head to head
On dry-matter numbers, BSFL actually carry a higher protein concentration (often in the 35–45% range) but with a bit more fat (around 10–15%). Discoid roaches run leaner, lower fat, with a clean protein-to-fat profile that suits dragons prone to putting on weight. So the simple read is: BSFL = more protein density plus calcium; discoids = leaner protein plus bulk. For an active, growing dragon I lean on discoids for everyday volume; for bone support I reach for BSFL.
Calcium-to-phosphorus: the real differentiator
This is where I'll correct a common overstatement. Some sources imply discoids have a "favorable" ratio, in reality discoids sit near 1:1, which is still phosphorus-leaning, so I dust them with calcium and gut-load them on dark leafy greens to improve what they pass on. BSFL are the genuine exception: their built-in calcium means they can stand in as a low-supplementation feeder. If metabolic bone disease prevention is your priority (gravid females, fast-growing juveniles), BSFL win this category outright.
Digestibility and health
Both are soft enough to be gentle on the gut, which matters for juveniles, seniors, and any dragon recovering from illness. Discoids' low chitin makes them far easier to process than a cricket, and their leanness suits everyday feeding. BSFL are equally digestible and add a little moisture, useful for dragons kept in very dry enclosures, but their higher fat means portion control matters for sedentary or overweight animals. Neither poses much impaction risk because of their soft bodies.
Cost, sourcing, and care
| Discoid roaches | Black soldier fly larvae | |
|---|---|---|
| Upfront cost | Higher (colony stock) | Low per serving |
| Long-term cost | Drops to near-zero if you breed | Ongoing per purchase |
| Breed at home? | Yes, easily | Not practical |
| Storage | Warm bin, 85–95°F, egg-crate hides | Cool, ~50–55°F (fridge), keep bedding slightly moist |
| Shelf life | Long-lived | Shorter; pupate if warm |
Discoids are the better long game: a starter colony in a warm, smooth-sided bin with egg-crate hides and a water-gel dish becomes a self-renewing supply, no more reordering. If you'd rather start a colony than rebuy, the discoid roach collection at All Angles Creatures is where I get breeding stock. BSFL are the convenience option: buy a cup, store it cold, use it, repeat.
My take: feed both, for different jobs
I don't treat this as either/or. I use discoid roaches as the everyday protein staple (cheap once the colony runs, lean, and dragons love chasing them) and BSFL as targeted calcium support for juveniles, gravid females, or any dragon I want to bump bone-wise without piling on supplement powder. Rotating the two also keeps mealtime interesting, dragons are visual hunters and a mix of a slow, chunky roach and a wriggling larva keeps them engaged.
A few mistakes to avoid with either: gut-load discoids 24–48 hours before feeding (un-fed feeders pass on little nutrition), never offer prey larger than the space between your dragon's eyes, keep both feeders' containers clean to avoid contamination, and don't let "BSFL are calcium-rich" make you neglect overall variety and vitamin D3.
For the long version on keeping a roach colony productive, see my guide on how to keep discoid roaches alive, and if you're weighing other feeders, are superworms safe for bearded dragons covers a popular treat insect.