24-hour minimum: Feeder insects pass their gut contents in roughly 12–24 hours. Any gut-load eaten less than 12 hours before feeding has not fully transferred its nutrients. Start gut-loading the day before you plan to feed, not the morning of.
Excellent gut-load foods
Fruit fly media (commercial mix)
A good commercial Drosophila media already balances nutrition for the culture; some keepers add a pinch of bee pollen or spirulina to boost the nutritional value passed on to the gecko.
Bee pollen granules (crushed, in fruit fly media)
Boosts protein and micronutrient content of the fruit fly culture, mirroring the pollen this species would encounter foraging on flowers in the wild.
Good options
Mashed sweet potato / carrot (in springtail/cricket culture)
Good beta-carotene and energy source for any live feeder culture being kept for pinhead crickets or supplemental springtails.
Oats / rolled oats
Good dry gut-load base for a cricket culture, keeping insects active without adding excess moisture.
What to avoid
Spinach
High oxalate content binds calcium in the feeder's gut — counterproductive if gut-loading for calcium content.
Citrus fruits
High acid content stresses feeder insects and may cause them to die before feeding.
Avocado
Toxic to many insects and will kill your feeders before they reach your gecko.
How to gut-load different feeders
Dubia roaches
The easiest to gut-load. They have a large digestive tract and hold nutrients well. Place gut-load food in the bin 24–48 hours before feeding. Remove uneaten soft food after 24 hours to prevent mould.
Crickets
Gut-load for 24 hours minimum in a separate ventilated container. Crickets drown easily — keep water in gel crystals or fresh vegetables rather than an open dish. Overloading crickets causes them to die and spoil quickly.
Mealworms
Gut-load in a shallow tray with bran or oat base plus a piece of sweet potato or carrot as a moisture source. Change the moisture source every 2 days to prevent mould. Mealworms transfer gut-load nutrients less efficiently than roaches.
Waxworms / treat feeders
Do not gut-load waxworms — they are in a pupal stage and do not feed. Offer them as-is, sparingly, and not more than once or twice per month. Their value is as a high-fat treat, not a nutritional staple.
Hydration tip: Many insects get their moisture from fresh vegetables in the gut-load. A dehydrated feeder insect passes that dehydration on to your gecko. Always include a moist component — sweet potato, carrot, or collard greens — in every gut-load mix.