House Flies vs. Discoid Roaches: Which Feeder Is Better for Blue Tongue Skinks?
I've kept blue tongue skinks long enough to know that the feeder question comes up constantly: house flies or discoid roaches? Both get recommended online, but they are not interchangeable. One is a meaty staple you can build a diet around; the other is a fast-moving snack that's great for enrichment and almost useless as a main course. Here's how I actually compare them, and how I feed both.
What a blue tongue skink actually needs
Blue tongues (Tiliqua species) are opportunistic omnivores from Australia and Indonesia. In captivity I aim for roughly half plant matter, half animal protein, adjusted for the individual animal's age and weight. Growing juveniles lean more toward protein; mature, sedentary adults lean toward greens to avoid obesity.
The animal-protein half is where feeders come in. The two numbers I care about most are fat (because blue tongues get fat easily in captivity) and the calcium-to-phosphorus ratio (because metabolic bone disease is the classic, preventable killer). Here's the honest version of the nutrition: nearly every feeder insect, including discoid roaches, is phosphorus-heavy and needs calcium added. Don't trust any source that tells you a feeder has a "favorable" Ca:P that lets you skip dusting — that's a myth that puts bones at risk.
My supplement routine
- Plain calcium carbonate (no D3) dusted on most insect feedings.
- Calcium with D3, or a reptile multivitamin, once a week — less often if the skink has strong UVB.
- Gut-load the feeders for 24-48 hours before offering them, so the nutrition starts inside the bug.
House flies: a snack, not a staple
House flies (Musca domestica) are soft-bodied, fast, and genuinely fun to watch a skink chase. On a dry-weight basis they're protein-rich (commonly cited around 60-70% protein, 10-20% fat by dry weight), but the operative word is small. A single fly is a crumb. For an adult blue tongue with a real appetite, you'd need a swarm to make a meal, and they're slippery to manage.
Where flies earn their place
- Enrichment. Their erratic flight triggers hunting behavior in a way a slow roach can't.
- Tiny mouths. Hatchlings and very small juveniles can take flies easily.
- Variety. Texture and movement that's different from everything else in rotation.
The catch
Flies don't satiate an adult. Their calcium is low, so dusting is mandatory. And hygiene is everything — flies from your kitchen or yard can carry parasites and pesticide residue. I only use flies raised from clean cultures or reptile-safe pupae, never wild-caught.
Discoid roaches: the workhorse staple
Discoid roaches (Blaberus discoidalis — not Blaptica dubia, a different species people constantly confuse them with) are my default insect for blue tongues. They're large enough to be a real meal, available in a full size range from pinhead nymphs to big adults, and they take gut-load beautifully.
Two practical traits make them ideal colony bugs: they can't climb smooth surfaces (a smooth-walled bin holds them with no lid gymnastics), and the adults essentially don't fly in normal keeping conditions. They're quiet and low-odor compared to crickets. For a busy keeper, that's the difference between a feeder you maintain and one you give up on.
On nutrition, discoids are solidly protein-rich and moderate in fat — a good staple profile. But the same rule applies: dust them. Their raw Ca:P is phosphorus-heavy like every other roach. The advantage isn't magic calcium; it's that they gut-load so well that you can pack real nutrition into them before feeding.
You can source them from my shop's discoid roach collection in the size that matches your skink.
Head to head
| Factor | House flies | Discoid roaches |
|---|---|---|
| Meal size | Tiny — snack only | Substantial — true staple |
| Protein | High (dry weight) | High |
| Fat | Low | Moderate |
| Calcium (undusted) | Low — must dust | Low — must dust |
| Gut-loading | Limited | Excellent |
| Escape risk | High (fast, fly) | Low (can't climb glass, don't fly) |
| Odor / noise | Moderate | Low |
| Best role | Enrichment, hatchlings | Staple feeder |
The verdict isn't close for a primary feeder: discoid roaches win. House flies are a worthwhile rotation item for stimulation and for the smallest animals, but they can't carry the diet.
Safety: parasites, pesticides, and sizing
Three risks matter regardless of which bug you pick.
- Parasites. Most common with wild-caught flies, but any feeder raised in filth can carry pathogens. Buy from clean sources and quarantine new feeders before they go into your colony.
- Pesticides. A fly that walked through treated areas can poison a skink. This alone disqualifies wild flies.
- Sizing. Prey wider than the gap between the skink's eyes risks choking and gut impaction. Match feeder size to the animal, and offer with tongs so you control what goes in.
How I actually rotate feeders
I don't feed one bug forever. A typical week for an adult blue tongue is a base of dusted discoid roaches a few times across the week, the occasional fly session for enrichment, and a rotation that also touches other feeders — plus the all-important plant half of the diet (collard, dandelion, and mustard greens, squash, with fruit only as an occasional treat). Variety covers the gaps that any single feeder leaves.
For the full colony-keeping side — how I house, gut-load, and breed discoids so I never run out — see my guide on keeping discoid roaches alive. For more on where discoids come from and why they behave the way they do, read the native habitat of discoid roaches.
Metabolic bone disease and reptile calcium needs are well documented in the Merck Veterinary Manual's reptile nutrition section, which is worth reading once so the supplement routine makes sense rather than feeling arbitrary.
Keep going: pair this with how to keep discoid roaches alive and the exotic animals hub for the rest of the feeder library.