Feeder insects are the foundation of the diet for most reptiles, amphibians and inverts in the hobby — and also the part new keepers most often get wrong. Not because insects are hard to buy, but because a cricket, straight from the tub, is not the balanced meal it looks like. Left to their own devices, feeder insects are low in calcium and awkwardly high in phosphorus, which is a recipe for slow, avoidable health problems in the animal eating them. The good news is that two simple habits — gut-loading and dusting — turn a mediocre feeder into a genuinely nourishing one. This guide explains both, compares the common feeders, and shows you how to build a varied diet that keeps your animal in top condition.
Think of it this way: your reptile is not really eating the insect, it is eating whatever the insect is made of and whatever is in its gut. That single idea explains everything that follows. Look after your feeders, and they look after your animal.
Why feeder insects need help
Insects evolved to be eaten, but not to be a complete diet on their own in a glass box. The central problem is the ratio of calcium to phosphorus. Reptiles need noticeably more calcium than phosphorus in their diet, yet most feeder insects have the balance the wrong way round — plenty of phosphorus, very little calcium. Over weeks and months, a diet that is chronically short of calcium (and of the vitamin D3 needed to absorb it) leads to metabolic bone disease: soft, deformed bones, tremors and, untreated, a slow decline. It is one of the most common health problems in captive reptiles, and it is almost entirely preventable at feeding time.
That is what gut-loading and dusting are for. Gut-loading improves what is inside the insect; dusting adds minerals to the outside. Do both as a matter of routine and you close the nutritional gap that causes so much trouble.
Gut-loading: feeding your feeders
Gut-loading simply means feeding your insects well before you feed them to your pet, so their digestive tract is packed with nutritious food at the moment they are eaten. A cricket that has spent a day grazing on fresh greens and a quality gut-load is a small parcel of vitamins and moisture; a cricket kept in a bare tub on nothing is little more than an empty, crunchy shell.
The window that matters is the twenty-four to forty-eight hours before feeding. In that time, give your feeders a spread of fresh vegetables and leafy greens — collard greens, dandelion, squash, carrot, sweet potato — alongside a commercial gut-load if you use one. Provide hydration too, ideally through water crystals or a bug gel rather than an open dish they can drown in. Avoid loading up on anything high in phosphorus or oxalates; the aim is to raise the insect’s calcium and vitamin content, not undo your good work.
Keeper’s tip: Gut-loading is not something you do in a panic ten minutes before feeding. Keep your feeders permanently on good food and water, so they are “loaded” whenever you reach for them. A well-run feeder tub is the cheapest health insurance your animal will ever get.
Dusting: the mineral coat
Dusting is the final step, done moments before the insects go in. You place a few feeders in a tub or bag, add a small pinch of supplement powder, and gently shake until they are lightly coated — like tossing chips in salt. Then you feed them straight away, because the powder starts to fall off within minutes and fastidious insects will groom it away if given the chance.
There are three kinds of supplement, and knowing when to use each is most of the skill:
| Supplement | What it does | Roughly how often |
|---|---|---|
| Plain calcium (no D3) | Corrects the calcium shortfall in insects | Most feedings, especially for UVB-lit animals |
| Calcium with D3 | Adds the vitamin D3 needed to absorb calcium | Once or twice a week for animals without UVB |
| Multivitamin | Fills wider vitamin and mineral gaps | Around once a week to once a fortnight |
The exact rhythm depends on your species, its age and whether it has UVB lighting. Fast-growing juveniles need calcium at almost every feed; settled adults need it a little less often. Animals that get good UVB can make their own vitamin D3 and so need less of it dusted on, while those kept without UVB rely on calcium-with-D3 to cover the gap — but D3 is a case of enough, not more, since a heavy hand with it causes its own problems. When in doubt, plain calcium most of the time, D3 and multivitamin as regular top-ups, is a safe pattern for the majority of insectivores. If UVB is new to you, our crested gecko care guide talks through how lighting and supplements interact.
The common feeders, compared
No single insect is the perfect food, which is exactly why variety matters. Each feeder brings something different to the table, and rotating a few of them gives a broader, more resilient diet than leaning on any one. Here is how the usual suspects stack up.
| Feeder | Best for | Watch out for |
|---|---|---|
| Brown/banded crickets | A cheap, active staple that triggers hunting | Poor calcium ratio; noisy; will nibble a sleeping animal if left in |
| Dubia roaches | High protein, easy to keep, quiet and odourless | Slower-moving, so less of a “chase” for some animals |
| Locusts | Larger prey for bigger lizards; very active | Pricier; size them carefully |
| Black soldier fly larvae | Naturally calcium-rich — the rare well-balanced feeder | Small; best as part of a mix, not the whole diet |
| Mealworms | Convenient treat; long shelf life | High fat and tough skins — a treat, not a staple |
| Waxworms | Fatty pick-me-up for underweight animals | Very high fat; strictly an occasional indulgence |
A couple of these deserve a word more. Crickets remain the classic staple for good reason — cheap, widely available and irresistibly twitchy — but they have that inverted calcium-to-phosphorus ratio, so they lean hard on your dusting and gut-loading to become a good meal. Dubia roaches are the quiet favourite of experienced keepers: high in protein, low in odour, unable to climb smooth surfaces or infest a British home, and easy to breed into a self-sustaining colony. Black soldier fly larvae (sold as calciworms) are the genuine exception to the calcium rule, coming pre-loaded with the mineral, which makes them a brilliant addition to a rotation. Mealworms and waxworms, by contrast, are the sweets of the feeder world — fine now and then, poor as a daily staple.
Getting the size right
However well you feed and dust an insect, an oversized one is dangerous. The rule keepers live by is simple: never offer a feeder longer than the space between your animal’s eyes. Anything bigger risks choking or gut impaction, particularly in small or young animals. It is always safer to feed several smaller insects than one large one, and to size down for hatchlings. When in doubt, go smaller.
Keeping your feeders alive and well
A tub of insects is a small livestock project in its own right, and a few minutes of care keeps them nutritious. House them in a ventilated container with egg-flat cardboard for surface area and hiding, at the warmth the species prefers, with their gut-load food and a spill-proof water source always available. Remove any dead ones promptly, and don’t overcrowd them. Feeders kept like this stay plump, active and full of goodness; feeders left to starve in a hot, bare tub lose condition fast and pass that poverty straight to your pet.
Keeper’s tip: Never leave loose crickets or locusts in an enclosure overnight. Uneaten crickets will hide, stress your animal and, given the chance, nibble at its skin, toes and eyes while it sleeps. Feed what will be eaten in a sitting, and remove the stragglers.
Any insects that do escape into a bioactive enclosure are usually cleaned up by the resident crew, but that is a safety net, not a feeding strategy. If you are running a living vivarium, our guides on setting up a bioactive terrarium and keeping isopods as a clean-up crew explain how that mop-up crew works.
Building a varied diet
If you take one thing from this guide, let it be variety. Rotating three or four feeders — say dubia roaches and crickets as staples, with locusts and calciworms for variety — gives a broader nutritional profile than any single insect can, and it stops fussy animals fixating on one food and refusing everything else. Layer gut-loading and sensible dusting on top of that rotation, size everything correctly, and you have covered the vast majority of what an insectivorous reptile needs from its diet. The rest is watching your animal thrive on it.
Frequently asked questions
What’s the difference between gut-loading and dusting?
Gut-loading means feeding your insects nutritious food for a day or two beforehand, so they are full of goodness on the inside. Dusting means coating them in a mineral or vitamin powder just before feeding. They tackle different gaps, so the best practice is to do both.
How often should I use calcium with D3 versus plain calcium?
Use plain calcium at most feeds to fix the insects’ calcium shortfall. Add vitamin D3 (as calcium-with-D3) roughly once or twice a week for animals kept without UVB, since they can’t make their own D3. Animals with good UVB lighting need much less dusted D3. Don’t overdo D3 — enough is better than more.
Can I feed my reptile only mealworms?
No. Mealworms are high in fat and low in usable calcium, with tough skins, which makes them a treat rather than a staple. A mealworm-only diet is a classic cause of obesity and metabolic bone disease. Use them occasionally within a varied, dusted, gut-loaded rotation.
Are dubia roaches better than crickets?
Nutritionally they have the edge — more protein, a better protein-to-fat ratio, and they’re quiet, odourless and easy to keep. Crickets are cheaper, more active and easier to buy, which many animals find more stimulating to hunt. The best answer for most keepers is to offer both.
How big should a feeder insect be?
No longer than the gap between your animal’s eyes. Oversized prey risks choking and impaction, especially in juveniles. Several small feeders are always safer than one large one.
Do I still need to dust insects if my reptile has UVB?
Usually yes — UVB helps your animal make vitamin D3, but it does nothing to fix the low calcium in the insects themselves. Keep dusting with plain calcium; you’ll simply need less added D3 than an animal kept without UVB.