Why feeding too early is risky
During a moult the tarantula sheds the old exoskeleton, including the lining of structures associated with feeding. The new cuticle begins soft and gradually hardens. Offering a cricket or roach while the spider is still soft creates a needless risk of injury.
The spider does not need an immediate meal to recover. Water and quiet are more important in the first stage after a successful moult. Remove any feeder insects that were left in the enclosure before the moult began.
Check fang colour before feeding
Fresh fangs can look pale, translucent or reddish. As they harden they darken substantially, eventually appearing black. That visual change is a better practical cue than assuming every tarantula is ready on day five or day seven.
You may not be able to inspect the fangs of a reclusive fossorial spider. In that case, give it more time rather than digging it out for a closer look. An extra few days of fasting is normally far less risky than feeding too soon.
Slings harden faster than giant adults
Tiny slings generally harden much more quickly than large adults because there is less new exoskeleton to harden. A small fast-growing sling may be ready for appropriately tiny prey relatively soon, while a giant adult can need a substantially longer rest.
This is why fixed internet rules are unreliable. Life stage, size, species and individual condition all matter. Use the individual spider rather than a countdown copied from somebody else's animal.
What to do during the waiting period
Keep the water source available, avoid handling and do not redesign the enclosure. The spider may stretch, groom, drink or remain very still. Those behaviours can all be normal after a moult.
If the spider has moulted inside a sealed retreat, leave the retreat intact. It will usually reopen the burrow when it is ready to resume normal activity. Do not interpret a closed door as a request for help.
Choosing the first post-moult meal
Start with a sensibly sized feeder rather than the largest prey the spider can overpower. The first meal is not a test of strength. For slings, appropriately small or pre-killed prey can be easier to manage; for larger spiders, normal feeder insects are fine once hardening is complete.
If the spider ignores the first offering, remove it and try again later. A successful moult does not force an immediate return of appetite.
When something looks wrong
A spider that cannot right itself, remains trapped in old exoskeleton, is leaking haemolymph or shows a sustained abnormal posture needs a different assessment from a healthy spider that simply has not eaten. Those are injury or failed-moult concerns, not feeding-schedule questions.
If there is significant injury or persistent dysfunction, seek experienced exotic-veterinary advice where available. Do not use live prey as a way of testing whether the spider is healthy.
What the old moult can tell you
The discarded exuvia is useful evidence that a true moult has occurred, especially when the spider completed it out of sight. If it is accessible without disturbing the animal, you can remove it later for sexing or records. There is no need to wrestle it away while the spider is still soft.
A tarantula may sit near or even manipulate the old moult for a while. Let the spider move away on its own before trying to tidy the enclosure.
Drinking after a moult
Many tarantulas drink after moulting. Make sure the water dish is clean and easy to reach. For tiny slings, maintain the species-appropriate moisture strategy so they are not left in a completely desiccated micro-enclosure while hardening.
Do not flood the enclosure because the spider has moulted. Stable conditions are still the goal. Sudden soaking can create its own set of problems with mould, ventilation and substrate condition.
What if the abdomen looks smaller?
A newly moulted tarantula often looks longer-legged and slimmer, with an abdomen that appears reduced compared with the pre-moult animal. That alone is not a reason to feed before the fangs are ready.
Once hardening is complete, normal feeding can rebuild body condition gradually. There is no need to compensate for the moult with oversized prey or unusually frequent meals.
Keep your own post-moult records
Record the moult date and the date the spider successfully takes its first meal. Over several moults, that gives you an individual pattern for the animal and is more useful than somebody else's fixed schedule.
Those records are especially valuable in a large collection because species, size and individual behaviour vary so much. A simple note prevents you from guessing which spider moulted when.
Large adults need extra patience
The largest terrestrial species can take noticeably longer to harden than slings and small juveniles. Their body size makes the visual change in the fangs especially useful. Do not let a strong pre-moult feeding response convince you that a huge adult needs food immediately after emerging.
Waiting until hardening is obvious also protects the new fangs. A tarantula can go without food far longer than it can safely fight a feeder while its mouthparts are still soft.