Discoid Roaches vs House Flies: The Better Feeder for Blue Tongue Skinks
I keep blue tongue skinks, and "discoid roaches vs house flies" is one of those comparisons that sounds balanced but isn't. One is a legitimate staple; the other is a niche enrichment item with real hygiene baggage. Here's the straight version, with the calcium and disease claims corrected.
What blue tongue skinks need from protein
Blue tongues (Tiliqua spp.) are omnivores. Insects and other animal protein make up roughly half their diet, the rest being leafy greens with a little fruit. The protein source needs to be:
- Nutrient-dense — enough protein per bite to actually feed a stocky lizard.
- Digestible — low chitin, soft-bodied, because skinks digest slowly and impaction is a risk.
- Clean and safe — free of the pesticides, bacteria and parasites that wild insects carry.
- Calcium-supplemented — dusted with calcium/D3 to prevent metabolic bone disease (MBD).
Measured against that list, the two feeders diverge fast.
Discoid roaches
Discoid roaches (Blaberus discoidalis) are a non-climbing, non-flying tropical roach from Central and South America — and they're frequently confused with dubia roaches (Blaptica dubia), which are a separate species. For blue tongues they check almost every box:
- Protein ~20-23%, fat ~7-10%, moisture ~65-70% — dense, lean, and substantial.
- High meat-to-shell ratio and low chitin, so one roach delivers real nutrition and digests easily.
- Larger size suits a skink's crushing jaws; size the roach to the animal.
- Clean and low-maintenance — quiet, odorless, hardy, easy to breed, and from a reputable breeder they're free of contaminants.
- Can't climb smooth surfaces and can't fly, so a smooth-sided bin holds the colony and they can't infest a temperate home.
The one claim to correct: discoid roaches do not carry a favorable 2:1 (or 1:1) calcium-to-phosphorus ratio. That number gets repeated everywhere and it's wrong. Like nearly every feeder, discoids are phosphorus-heavy and need calcium dusting. Their real strengths are protein, digestibility, and clean keeping — not minerals. (If you want a feeder that genuinely supplies its own calcium, that's black soldier fly larvae, the lone exception.)
Buy them captive-bred from All Angles Creatures' discoid roach collection.
House flies
House flies (Musca domestica) come up because they're cheap and high in protein for their size. But for a blue tongue skink the case falls apart:
- Tiny yield. A skink would need an impractical number of flies to make a meal. Most of the "nutrition" is offset by how few calories one fly delivers.
- Phosphorus-heavy too, and with an even less useful overall profile than roaches — supplementation is mandatory if you use them at all.
- Hygiene risk. Flies are scavengers that breed on decaying matter. Wild-caught flies are a genuine vector for bacteria and parasites. Captive cultures reduce that risk but take real effort.
- Hard to manage. Fast, erratic, prone to escaping and becoming a household nuisance.
Their one upside is enrichment: the erratic flight can trigger a skink's hunting instinct. That's the entire argument for them — a bit of stimulation, not a meal.
Head to head
| Factor | Discoid roach | House fly |
|---|---|---|
| Protein per bug | High (large, meaty) | Low (tiny) |
| Digestibility | Excellent (low chitin) | Poor value for size |
| Calcium balance | Phosphorus-heavy — dust it | Phosphorus-heavy — dust it |
| Safety | Clean from breeders | Disease/parasite risk, esp. wild |
| Ease of keeping | Easy; contained, odorless | Hard; escapes, short-lived |
| Role for skinks | Staple | Occasional enrichment only |
Feeding routine
- Gut-load roaches 24-48 hours ahead on carrots, squash, greens, or commercial chow.
- Dust with calcium + D3, especially when UVB is marginal — this is your MBD insurance.
- Size prey no wider than the skink's head; smaller for juveniles.
- Schedule: juveniles daily, adults every 2-3 days. Remove uneaten insects.
- Balance the bowl: pair protein with collard, mustard and dandelion greens, some squash and carrot, and occasional berries or mango. Avoid spinach and iceberg.
The verdict isn't close: feed discoid roaches as the staple, supplement with other proven feeders, and treat house flies as — at most — an occasional bit of hunting enrichment, never the diet.
For the three-way version of this question see discoid roaches, fruit flies, or crickets, or learn to run a colony with how to keep discoid roaches alive. On the calcium science behind MBD, I rely on the Merck Veterinary Manual on reptile nutrition.