Using the wrong enclosure style
Burgundy Goliath Birdeaters are terrestrial. Young spiders may dig more, while larger animals often spend more time in the open, although individual Theraphosa stirmi can still choose to remain hidden. Build the enclosure around that lifestyle instead of using the same shape for every tarantula.
For Theraphosa stirmi, adult size is about 25–28 cm (10–11 in), but enclosure size should still follow the spider's current size. A sling does not benefit from being placed straight into a large adult setup.
Getting moisture wrong
For Burgundy Goliath Birdeaters, use moisture-retentive substrate with strong ventilation. Damp rather than waterlogged. The mistake is usually treating the whole enclosure as either permanently wet or permanently dry instead of watching how the substrate actually behaves.
Keep fresh water available to Theraphosa stirmi. Persistent condensation, a stale smell or wet substrate that never dries are reasons to reduce water or improve airflow.
Overfeeding or chasing a schedule
Feed Burgundy Goliath Birdeaters according to size, appetite and abdomen, not because a calendar says food is due. Theraphosa stirmi can refuse meals for normal reasons, especially around premoult.
Do not keep adding prey when a Burgundy Goliath Birdeater is already very well fed. Remove ignored live feeders and offer food again later.
Disturbing premoult or moulting
When Theraphosa stirmi shows premoult signs, remove live prey and leave the spider alone. A closed retreat is not an invitation to open it and check what is happening.
After a moult, wait until a Burgundy Goliath Birdeater has hardened and the fangs have darkened before feeding. Larger spiders usually need longer than tiny slings.
Making maintenance too difficult
A good Theraphosa stirmi enclosure lets you refill water and remove food remains without dismantling the main retreat. If every job requires moving cork, digging into substrate or working directly over the spider, change the layout.
Handling is not part of routine care for Burgundy Goliath Birdeaters. Use long tools when useful and have a catch cup ready for rehousing.
Changing too much at once
Once a Burgundy Goliath Birdeater has settled, avoid repeatedly rearranging the enclosure for appearance. Stable housing usually matters more to Theraphosa stirmi than a constantly changing display.
If something needs correcting, change one clear husbandry problem at a time. That makes it easier to see whether Theraphosa stirmi settles, feeds and uses the enclosure normally afterward.