Recognising premoult
Food refusal is one common premoult sign in Grammostola grossa, especially when it appears alongside heavier webbing, retreat closure or a darker exposed abdomen. Not every Guarani Giant shows every sign.
Once premoult looks likely, stop offering live prey and keep fresh water available. Do not keep testing Grammostola grossa's appetite every day.
Preparing the enclosure
Leave the main retreat intact for Grammostola grossa. Remove loose feeders, check the water dish and avoid unnecessary rehousing or major enclosure work while the spider is preparing to moult.
Stable temperature and normal moisture are more useful than sudden changes. Keep Grammostola grossa within its normal range of 19–25°C and follow the usual moisture pattern for the species.
During the moult
A Guarani Giant may moult on its back, side or in another position that looks unusual to a new keeper. Do not flip the spider over or touch it simply because the posture looks alarming.
Give Grammostola grossa space. Intervention during a normal moult can cause more harm than leaving the spider alone, so watch from outside the enclosure unless there is a clear, specific emergency.
After the moult
After Grammostola grossa emerges, the new exoskeleton and fangs are soft. Keep water available and wait for the spider to harden before offering food.
Small Guarani Giants harden sooner than large adults. Instead of using one fixed number of days for every spider, wait until movement looks normal and the fangs have darkened.
Using the exuvia
A well-preserved moult from Grammostola grossa can be useful for confirming sex and keeping growth records. Remove it only when doing so will not disturb the spider.
Date the exuvia if you keep records for a Guarani Giant. Over time, moult dates provide a much clearer picture of growth than trying to estimate age from size alone.
When a delay is normal
Premoult can last much longer in a large Grammostola grossa than in a tiny sling. A period of hiding and fasting is not automatically a failed moult or an emergency.
Keep the enclosure stable and watch for actual problems rather than the passage of time alone. If a Guarani Giant is secure, has water and is behaving like a premoult spider, patience is usually the right response.