Superworm Diet, Nutrition & Care: A Keeper's Complete Guide

Superworms are one of the most misunderstood feeders in the hobby. People treat them like a staple because the animals love them, then a year later they've got an overweight bearded dragon and a vet bill. Or they buy a tub, stick it in the fridge to "keep them fresh" the way you would mealworms, and kill the whole batch in three days. Or they refuse to use them at all because a forum told them superworms cause impaction and chew their way out of an animal's stomach — most of which is myth.

I've fed superworms (Zophobas morio) for years across a range of animals, and the truth is they're a fantastic feeder when you understand what they are: a large, soft-bodied, high-fat, high-palatability treat that you keep at room temperature, gut-load before serving, and size carefully. Get those few things right and they're one of the most useful tools in your feeder rotation. Get them wrong and they cause exactly the problems they're famous for.

This is the complete guide: what superworms actually are, their real nutrition (with a comparison table against the other common feeders), how to gut-load them so they're worth feeding, feeding schedules and sizing by animal, the impaction and "chew-out" myths sorted from the real cautions, and how to keep a tub alive for months — including why they refuse to turn into beetles until you make them. Read it once and you'll never misuse a superworm again.

What a superworm actually is

A superworm is the larval stage of a darkling beetle, Zophobas morio, native to Central and South America. It is not a giant mealworm, even though it looks like one and people sell them as if they're interchangeable. Mealworms are the larvae of a different, smaller darkling beetle (Tenebrio molitor), and the two behave completely differently in ways that matter for how you keep and feed them.

A full-grown superworm runs about 1.5 to 2.25 inches (40-60 mm) long and noticeably thicker than a mealworm — roughly the diameter of a coffee stirrer or a bit more. The body is segmented, tan-to-cream with darker bands at each segment joint, and tipped with a small but genuinely hard, dark head capsule with working mandibles. That head capsule is the whole reason superworms have a reputation: it's the hardest part of the animal, and it's where the "they bite" and "they cause impaction" stories come from. We'll deal with both honestly below.

Like all darkling beetles, Zophobas goes through complete metamorphosis: egg → larva (the "superworm" you buy) → pupa → adult beetle. The larval stage is the long one and the one we feed from. Here's the quirk that surprises everyone the first time: a superworm larva will not pupate as long as it's crowded in a bin with other worms and food around it. Being packed together chemically and behaviorally suppresses metamorphosis. That's a survival adaptation — in a crowded patch a larva that pupated would just get eaten — and for keepers it's a gift, because it's exactly why a tub of superworms sits on your shelf for months without turning into a tub of beetles. To make them pupate (for breeding) you have to deliberately isolate them, which I'll cover in the breeding section.

Superworm vs. mealworm — the differences that matter

People constantly conflate these two. The practical differences:

• ◆Size. Superworms are 2-4x the mass of a mealworm. That makes them a feeder for larger animals and a poor fit for small geckos and juveniles.
• ◆The fridge. This is the big one. Mealworms can be refrigerated to slow them down and keep them for weeks. Superworms cannot — cold kills them. Refrigerating a tub of superworms is the most common way keepers accidentally wipe out a batch. Keep them at room temperature, always.
• ◆Exoskeleton. Superworms are softer-bodied along the trunk than their size suggests, but they have that harder head capsule. Mealworms are smaller and proportionally a bit harder overall for their size.
• ◆Pupation behavior. Both suppress pupation in a crowd, but the superworm's isolate-to-pupate trick is more pronounced and is the standard breeding method.

If you only remember two things from this section: superworms are a large feeder, and never put them in the fridge.

The real nutrition: why superworms are a treat, not a staple

This is the part the animals don't get a vote on. Superworms taste like candy to a reptile — they're soft, wriggly, and fatty, and almost everything that eats insects will gorge on them. That palatability is exactly why they're dangerous as a staple: left to their own preferences, most animals would eat superworms until they were obese, and you're the one who has to say no.

Macronutrients

On an as-fed (live) basis — which is what actually matters, because you feed them wet, not dried — superworms run approximately:

• ◆Protein: ~19-20% — solid, comparable to crickets and roaches.
• ◆Fat: ~14-17% — this is the headline number. It's roughly double to triple the fat of a cricket, and it's why superworms are calorie bombs.
• ◆Moisture: ~58-60% — fairly typical for a feeder larva.
• ◆Fiber/chitin: low-to-moderate in the body, concentrated in that head capsule.

You'll often see superworms quoted at "40-50% protein," and that number isn't wrong — it's just dry-matter protein, measured after all the water is removed. Once you account for the ~60% of the live worm that's water, the as-fed protein your animal actually eats lands around 19-20%. The same correction applies to fat: very high on a dry basis, ~15% as-fed. Always compare feeders on an as-fed basis or you'll badly misjudge them.

Micronutrients and the calcium problem

Like essentially every feeder insect, superworms have far more phosphorus than calcium — a calcium-to-phosphorus (Ca:P) ratio somewhere in the neighborhood of 1:12 to 1:18, which is badly inverted for reptiles and amphibians that need roughly 1:1 to 2:1 in favor of calcium for healthy bone. Fed without correction, a superworm-heavy diet pushes animals toward metabolic bone disease.

There are two levers to fix this, and you use both:

1. ◆Gut-load the worms with calcium-rich food before feeding (details below).
2. ◆Dust the worms with a calcium powder right before they go in the bowl.

Superworms also carry trace amounts of iron, magnesium, zinc, and some B-vitamins, but they're naturally low in vitamin A and the right calcium balance — which is the whole reason gut-loading and dusting aren't optional extras, they're the core of using this feeder responsibly.

How superworms compare to the other common feeders

Here's roughly how the staples and treats stack up. Treat these as approximate, as-fed figures — real values swing with diet, life stage, and source — but the relationships are reliable, and the relationships are what should drive your choices:

The takeaways that actually change what you do:

• ◆Superworms are the fattiest of the worms. That fat is a feature for an underweight, recovering, or breeding animal that needs to put on condition — and a liability for a healthy adult that doesn't. Use them where the calories help.
• ◆Build the diet on a low-fat staple — crickets, dubia, or discoid roaches — and rotate superworms in as a treat, not the base. If you keep a home colony, a discoid roach colony makes a far better staple to build that rotation around than any worm.
• ◆Black soldier fly larvae are the calcium counterweight. If you lean on fatty treats like superworms, having a naturally calcium-rich feeder in the rotation helps balance the bone-mineral math.
• ◆No single feeder is a complete diet. The healthiest insectivore diet is a rotation — a staple plus variety — and superworms are one excellent voice in that chorus, not the whole choir.

Gut-loading: making a superworm worth feeding

A superworm is a delivery vehicle. Whatever is sitting in its gut when your animal eats it gets transferred straight up the food chain. Feed the worm garbage and you're feeding your pet garbage in a worm-shaped wrapper; feed the worm well for a day or two and you're delivering real nutrition. This is the single highest-leverage habit in using superworms, and it costs almost nothing.

What gut-loading actually is

Gut-loading means giving feeders a nutrient-dense diet for 24-48 hours before they go to your animal. It's not the same as the maintenance diet you keep the tub on long-term — it's a deliberate, short, rich feeding right before service so the worms are full of good nutrients at the moment of feeding. Empty-gutted worms straight off the shelf are nutritionally hollow by comparison.

A working gut-load

A good gut-load has two parts:

• ◆A quality dry base. Wheat bran, rolled oats, or a commercial gut-load formula gives carbohydrate energy and fiber and doubles as bedding. Commercial gut-loads are formulated to push calcium and vitamins into the worm, which is exactly what you want for this feeder.
• ◆Fresh, moist produce. Carrot, sweet potato, squash, and dark leafy greens (collard, mustard, dandelion, kale) are the workhorses — they add moisture, vitamins, and, in the case of leafy greens, some calcium. Carrot and sweet potato also load beta-carotene (a vitamin-A precursor), which helps offset the worm's natural vitamin-A shortfall.

For the calcium problem specifically, you can offer calcium-rich greens during the gut-load, but the reliable fix is dusting — toss the gut-loaded worms in a calcium powder (plain calcium for routine feedings, calcium-plus-D3 or a multivitamin on the schedule your species needs) right before they go in the bowl. Gut-load and dust; don't rely on either alone for a feeder this phosphorus-heavy.

A small practical note on dusting superworms specifically: they're smooth and a little waxy compared to a cricket, so powder doesn't cling to them as well. Two tricks help — dust them in a small deli cup with a lid and give it a gentle swirl so they're evenly coated, and feed them immediately, because a superworm left sitting will groom or wipe most of the powder off within a few minutes. Dust at the bowl, not at the prep counter.

Why gut-loading beats "loading the worm" long-term

There's a meaningful difference between a worm that's been raised on a rich diet for weeks and a worm that's been gut-loaded for a day or two. Raising worms on heavy supplementation mostly changes their stored body fat — which you don't want more of — while a short, fresh gut-load fills the digestive tract with the vitamins, moisture, and calcium-rich material you actually want transferred to your pet. In other words, the value of gut-loading lives in the worm's gut, not its tissue, which is exactly why timing matters: a worm gut-loaded yesterday and fed today is full; a worm that ate well last month but has had an empty gut for two days is hollow again. Treat gut-loading as a pre-service ritual, every time, not a one-and-done.

What to skip during gut-loading

Don't bother with high-protein "boosts" like dog food, fish flakes, or heavy meat-meal for worms you're about to feed off. Those are sometimes used to push growth in worms you're raising, but they don't improve the nutrition delivered to your pet and they raise the worm's already-high fat and the risk of fouling the bin. Keep the pre-feeding gut-load to clean produce and grain, then dust.

Feeding off: sizing and schedules by animal

Matching worm size and feeding frequency to the animal is where most care advice goes vague. Here it is concretely. Two rules govern everything else:

The sizing rule: never feed a superworm longer than the space between your animal's eyes, and ideally no longer than the width of the animal's head. This is the real impaction safeguard (more on that below). Because adult superworms are big, that immediately rules them out for small animals.

The treat rule: superworms are a high-fat occasional item for almost everything that eats them. "A few, a few times a week" is the default posture; daily superworms is how you make a fat reptile.

By animal:

• ◆Bearded dragons (adults). This is the classic superworm customer. Adults handle the size well and love them. Offer a few superworms a couple of times a week as a treat alongside a staple-insect-and-greens diet — not as the daily protein. Watch body condition: a beardie with fat pads bulging and a thick tail base is getting too many. Always dust with calcium. Juvenile beardies need a lot of protein but are too small for full-size superworms — use appropriately small staple feeders and save superworms for when they've grown.
• ◆Leopard geckos and other medium-large geckos. A grown leopard gecko can take a properly sized superworm, but the size is borderline — pick smaller worms, feed one or two as an occasional treat every several days, not as the routine feeder. Their tail is a fat store; a leo with a tail wider than its neck is overweight, and fatty treats accelerate that. Dust with calcium.
• ◆Crested geckos. Mostly fed a complete powdered diet; superworms are an occasional enrichment/protein treat for adults only, and even then a single appropriately sized worm now and then. Many crested keepers skip them in favor of smaller insects.
• ◆Larger frogs and toads (Pacman frogs, large toads). Big amphibians take adult superworms readily — they're a good calorie-dense item. Feed to body condition; these animals will happily overeat. Every few days for adults is plenty.
• ◆Monitors, tegus, and large skinks. Superworms are a fine part of a varied carnivore diet. For larger individuals they're more of a topping or supplement than a meal — whole prey and other proteins carry the bulk.
• ◆Turtles (aquatic and box). Many will eat superworms enthusiastically as a treat alongside their staple diet. Same fat caution applies.
• ◆Birds and fish. Insectivorous birds and larger predatory fish take superworms as a high-energy treat. The fat content makes them valuable for birds in cold weather or breeding condition, but the same "treat not staple" logic holds.

The universal rule across all of them: size to the animal, dust with calcium, feed as a treat, and watch body condition. A fat reptile is the most common superworm mistake, and it's entirely preventable.

Hydration: the quiet variable

Hydration cuts two ways with superworms, and keepers usually only think about one of them.

For the worm: a superworm is roughly 60% water, and it gets that water from its food — there's no water dish in a superworm tub (an open dish just drowns them and fouls the bedding). The dry bran or oats they live in supplies no moisture at all, so the slice of carrot, potato, or squash sitting on top is their water source. Let that produce run out for too long and the worms slowly dehydrate, go limp, and stop feeding; pile too much wet produce in and you get mold, gnats, and grain mites. The target is a "just barely moist" environment — dry bedding with a single piece of fresh produce, replaced before it sours. Drier-but-fed beats damp-and-moldy every time.

For your animal: a well-hydrated worm is a small hydration delivery to whatever eats it, which matters more than people realize for desert species fed mostly dry insects. A superworm gut-loaded on carrot and squash carries useful moisture; a dried-out, neglected worm carries almost none. It's one more reason the pre-feeding gut-load isn't just about nutrients — it's also topping off the worm's water before it becomes part of your animal's meal.

The balance to strike, in one line: keep the bedding dry, keep one piece of fresh produce in at all times, and refresh it before it molds. That single habit covers both sides of the hydration equation.

Environmental factors that change how superworms feed and keep

Superworms are ectotherms — their whole metabolism rides on their environment — so a few ambient conditions quietly determine how well they eat, grow, and store. If a tub seems "off," it's almost always one of these four:

• ◆Temperature. The sweet spot for active feeding and steady growth is roughly 77-86°F (25-30°C). Cooler than that and they slow down, eat less, and develop sluggishly; hotter and you risk stress and dehydration. And the hard limit bears repeating one more time: cold kills them — there is no safe "slow them down in the fridge" move with superworms the way there is with mealworms.
• ◆Humidity. They want a moderate environment — roughly 40-60% relative humidity. Too dry and they desiccate and stop feeding; too damp and you're farming mold and mites instead of worms. The produce-on-dry-bedding setup naturally lands in a good range; you rarely need to manage humidity directly.
• ◆Light. Superworms are photophobic — they avoid light and feed best in the dark. A tub kept in dim, stable conditions will have worms actively feeding in the substrate; one under bright light will have worms burrowing and hiding instead of eating. This is also why an opaque or shaded tub keeps them calmer.
• ◆Food freshness. Stale, dried, or spoiled food drops their feeding rate fast. Fresh moist produce drives consumption and hydration; mushy, molding produce does the opposite and actively harms them. Freshness, not just presence, of food is what keeps a tub thriving.

None of this is hard — a dim shelf at room temperature with dry bedding and fresh carrot ticks every box — but knowing why each lever matters makes a struggling tub easy to diagnose.

The impaction and "chew-out" myths — sorted from the real cautions

Superworms carry more folklore than any other feeder, and a lot of it scares people off a perfectly good food. Let me separate what's real from what isn't.

Myth: superworms commonly cause impaction

Impaction — a blockage in the digestive tract — is a real and serious problem in reptiles, but the popular story that superworms' "indigestible exoskeleton" is a frequent cause is largely overblown. The far more common real causes of impaction are:

• ◆Temperatures too low to digest. Reptiles are ectotherms; they need the correct basking/ambient temperature to digest food at all. A beardie kept too cool can't process any feeder properly, and undigested food backs up. This is the number-one real cause and it gets blamed on the worm.
• ◆Dehydration. A dried-out gut moves food poorly.
• ◆Ingested substrate. Loose particulate substrate (sand, some loose beddings) swallowed during feeding is a genuine impaction risk — and is again wrongly blamed on the feeder.
• ◆Feeders too large. A worm longer than the space between the eyes is hard to process. This is the part of the impaction story that's true, and it's why the sizing rule exists.

So the honest version: a correctly sized superworm fed to a warm, hydrated animal off a non-particulate surface almost never causes impaction. Fix temperature, hydration, sizing, and feeding surface, and the worm is not the problem. The chitin in a single appropriately sized worm is a trivial fraction of a varied diet.

Myth: a swallowed superworm chews its way out of the stomach

This is the gory one, and it's a myth. The idea that a live superworm survives being swallowed and eats through the animal's stomach wall doesn't hold up — stomach acid and the swallowing process kill the worm within seconds. Healthy adult reptiles eat live superworms constantly with no such drama.

Crushing the head before feeding is therefore optional for most animals. Where it's reasonable: very small, very slow, sick, or recovering animals where you want to eliminate any chance of a defensive pinch on the way down, or animals that don't chew thoroughly. For a healthy adult beardie snapping worms in half, it's unnecessary.

Real caution: superworms bite

The thing that is true: superworms have functional mandibles and will pinch. They can nip you (mildly — startling more than damaging), and more importantly they can bite tankmates or a slow, sick animal. This is the actual reason behind the head-crushing advice — not stomach-chewing, but a defensive bite during a clumsy feeding. Don't leave loose superworms crawling in an enclosure with an animal that isn't actively hunting them; feed by tongs or in a feeding container, and remove uneaten worms.

Real caution: the fat

Worth repeating because it's the one that actually hurts animals: the genuine long-term risk of superworms isn't impaction or biting, it's obesity and hepatic lipidosis (fatty liver) from overfeeding a high-fat item. The myths get the attention; the fat does the damage. Respect the treat rule and you've handled the only caution that routinely matters.

Keeping superworms alive: storage and maintenance

Superworms are wonderfully low-maintenance to keep — far easier than crickets — as long as you don't make the two classic mistakes (the fridge, and overcrowding into a wet, moldy mess).

The setup

• ◆Container. A smooth-sided plastic tub with a ventilated lid. They can't climb smooth plastic, so they won't escape, but you do need airflow — drill or mesh some holes in the lid.
• ◆Bedding / food substrate. A thin layer (1-2 inches) of wheat bran or rolled oats. This is both their bedding and their food, so it doubles as a slow gut-load. Don't go deep — deep substrate traps moisture and hides problems.
• ◆Moisture. A slice of carrot, potato, or a chunk of squash laid on top supplies all the water they need. Do not use an open water dish — they'll drown and foul it. Replace the produce before it molds (every couple of days).

Temperature — and the fridge warning, again

Keep them at normal room temperature, ~70-80°F (21-27°C). Warmer makes them eat, grow, and move more; cooler slows them down. But there is a hard floor: cold kills superworms. Unlike mealworms, they have no cold-tolerant dormancy — chilling them, and especially refrigerating them, kills the batch within days. If your house gets cold, keep the tub somewhere stable and room-temperature. This single rule is the difference between a tub that lasts months and a tub that's dead by the weekend.

Maintenance rhythm

• ◆Replace produce every 2-3 days before it molds; pull anything slimy immediately.
• ◆Refresh the bran/oats when it turns mostly to fine frass (powdery waste) — sift the worms out, dump the old substrate, add fresh.
• ◆Don't overcrowd. Too many worms in a small tub means competition, stress, cannibalism of any soft (freshly molted or dead) individuals, and faster fouling. Give them room.
• ◆Remove the dead. A dead worm fouls fast and invites mold and mites. Pull any darkened, soft, or motionless worms.

Kept this way a tub of superworms stays in good shape for roughly two months — plenty of time to feed through a normal supply. When you need to restock, All Angles Creatures stocks healthy, well-started superworms sized for feeding.

Diet's effect on growth and size — for keepers who raise them

Most people just buy and feed superworms, but if you're holding or growing a batch, diet genuinely changes the worm. A few honest mechanics:

• ◆Carbohydrate-rich bedding (bran/oats) drives steady larval growth and energy stores, which is why it's the standard substrate. It's the engine of normal development.
• ◆Fresh produce adds moisture and vitamins and supports healthy molting; carrot and sweet potato in particular contribute beta-carotene.
• ◆Heavy protein supplementation (the dog-food / fish-meal trick some breeders use) can push growth and biomass, but it also raises the worm's fat, fouls the bin faster, and can trigger cannibalism if worms get protein-hungry. For a feeder you're about to use, it's not worth it — clean grain plus produce is better.
• ◆Overfeeding and poor diet backfire. Excess uneaten food molds, fouls the substrate, and stresses the colony, which slows growth. More food is not more growth past a point; clean, consistent food is.

The practical version for a keeper: bran or oats as bedding, carrot/sweet potato for moisture, sift and refresh when it turns to frass, don't overcrowd, and don't overfeed. That's it.

Breeding superworms — and the pupation trick

You don't need to breed superworms — they're cheap and a purchased tub lasts months — but it's genuinely interesting, and it's the only way to understand why your worms never spontaneously become beetles.

The key fact again: larvae suppress pupation as long as they're crowded together with food. To break that, you isolate them:

1. ◆Pick the largest larvae — the ones that have stopped growing and are ready.
2. ◆Put each one alone in a small dark container — the classic is an empty 35mm film canister, or any small lightless cup — with no food and no bedding. Isolation plus darkness plus no food is the trigger.
3. ◆Wait. Within a few days to a week the larva curls into a tight C-shape and stops moving. Over the next one to two weeks it pupates — turning into a pale, alien-looking pupa — and then ecloses into a darkling beetle.
4. ◆Move the beetles to a breeding bin with substrate (bran/oats with some egg-flat hides), keep it warm (~80°F) and lightly moist, and feed them produce. Beetles mate and lay eggs in the substrate.
5. ◆Eggs hatch into tiny larvae that grow over a few months back into feeding-size superworms, completing the loop.

It's a slower, fiddlier process than breeding roaches, which is why most keepers just buy superworms. But if you want the full cycle, isolation-to-pupate is the secret the bin-kept worms are hiding from you.

What the research actually says

It's worth knowing that the broad strokes here aren't hobby folklore — they line up with the published work on feeder-insect nutrition, and a couple of findings are genuinely useful to a keeper.

The foundational data on what's in a superworm comes from analytical studies of commercially raised feeder invertebrates — the same body of work that gives us the protein/fat/moisture and the badly inverted calcium-to-phosphorus numbers cited above. The consistent finding across that literature: feeder insects as a class are calcium-poor and phosphorus-rich, and superworms sit at the high-fat end of the group. That's not an opinion about superworms; it's a measurement, and it's the whole reason dusting and gut-loading exist as standard practice.

The second useful thread is research on manipulating feeder nutrition. Studies repeatedly show that what you feed an insect measurably changes its composition — gut-loading with calcium-fortified diets raises the calcium an animal actually receives, and high-protein versus high-carbohydrate substrates shift a larva's growth and biomass. The practical lesson isn't "feed superworms more protein to make them better feeders" — overdoing animal protein backfires with fouling and cannibalism — it's that the worm is genuinely plastic, so your gut-load and dusting choices have a real, documented effect on the nutrition delivered up the chain. That's empowering: it means a cheap feeder, handled well, becomes a meaningfully better one.

The third thread worth flagging is sustainability research, because it's why superworms are having a moment beyond the reptile hobby. Zophobas morio (and its relatives) are being studied for their ability to consume agricultural waste and even certain plastics, and for large-scale protein production. None of that changes how you feed your gecko, but it explains why superworm husbandry is suddenly a serious research subject and why the care information is steadily getting better.

The honest caveat on all of it: published as-fed values come from specific colonies on specific diets, so treat every number in this guide as a reliable ballpark, not a lab certificate for the worms in your tub. The relationships — high fat, poor calcium ratio, big size, room-temperature keeping — are rock solid. The decimal points are not.

Sourcing and starting with good worms

A feeder is only as good as the colony it came from, and superworms are easy to get wrong at the source.

• ◆Buy active, plump, evenly sized worms. Healthy superworms are firm, cream-colored with crisp dark banding, and actively wriggling when disturbed. Pass on batches with lots of dark, soft, motionless, or shriveled individuals, or any that smell sour — those are signs of a stressed, fouled, or chilled batch (cold-shocked superworms often arrive already dying).
• ◆Check for mites and mold on arrival. A dusting of tiny crawling specks on the worms or the bedding means grain mites came along for the ride. It's not a catastrophe, but you'll want to sift the worms into a clean tub with fresh dry bran rather than dumping the shipping substrate into your keeping container.
• ◆Acclimate, don't refrigerate. When a shipment arrives, bring the worms to a stable room temperature, move them into your prepared tub, and offer a slice of carrot. Resist any instinct to "store" them cold — by now you know that's the one thing that reliably kills them.
• ◆Match the size to your animal at purchase. Superworms are sold by size, and the giant ones are tempting because they look like the most food for the money. If your animal can't take a worm longer than the space between its eyes, buy a smaller grade rather than trying to feed off oversized worms.

A good first order of well-kept worms, set up in a clean dry tub at room temperature, will carry you for weeks of feeding with almost no effort.

Common problems and quick fixes

Work the likely causes in order:

• ◆Worms dying fast? Suspect cold first (the fridge, a cold room, a cold shipment), then a wet/molded bin from too much produce or too-deep damp substrate. Warm them to room temp, dry the bin out, remove dead worms and rotting food.
• ◆Mold or fungus gnats? Too wet. Cut back the produce, switch to a drier bedding, improve lid ventilation, and never let slimy food sit.
• ◆Tiny crawling specks (grain mites)? Also a too-wet signal. Dry the substrate, remove moist food, and if it's bad, sift the worms into a clean tub with fresh dry bran.
• ◆Worms shrinking / not growing? Usually too cold or out of food — warm them up and refresh the bran/oats.
• ◆Your animal got fat? The most common superworm "problem," and it's a feeding-schedule problem, not a worm problem. Cut superworms back to a true treat, lean on a low-fat staple, and let the animal slim down.
• ◆Worms biting each other / cannibalism? Overcrowded or protein-starved. Thin them out and make sure there's bran and produce available.

The short version

Superworms are a large, high-fat, soft-bodied treat — not a staple. Keep them at room temperature (never the fridge) in a ventilated tub with bran or oats and a slice of carrot. Before feeding, gut-load 24-48 hours on produce and grain and dust with calcium to fix their phosphorus-heavy mineral ratio. Size them to no longer than the space between your animal's eyes, feed a few a few times a week to larger insectivores, and watch body condition. Ignore the chew-through-the-stomach myth, take the impaction worry as a sizing-and-temperature reminder rather than a reason to avoid them, and respect the one caution that actually matters — the fat. Do that and superworms are one of the most useful, best-loved feeders you can keep.

Building a feeder rotation? A low-fat staple beats any treat as your base — see my full guide to keeping and breeding discoid roaches, or browse the complete feeder insect care library for hornworms, dubia, and the rest. For the science behind the nutrient numbers, the foundational reference is the University of Florida entomology department and Finke's complete nutrient composition study of feeder invertebrates.