Using the wrong enclosure style
Indian Ornamentals are arboreal, so spending time above the substrate, webbing around cork and using an elevated retreat are all normal for Poecilotheria regalis. Build the enclosure around that lifestyle instead of using the same shape for every tarantula.
For Poecilotheria regalis, adult size is about 17–18 cm (6.5–7 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 Indian Ornamentals, maintain moderate moisture with strong ventilation and constant access to clean water. 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 Poecilotheria regalis. 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 Indian Ornamentals according to size, appetite and abdomen, not because a calendar says food is due. Poecilotheria regalis can refuse meals for normal reasons, especially around premoult.
Do not keep adding prey when an Indian Ornamental is already very well fed. Remove ignored live feeders and offer food again later.
Disturbing premoult or moulting
When Poecilotheria regalis 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 an Indian Ornamental has hardened and the fangs have darkened before feeding. Larger spiders usually need longer than tiny slings.
Making maintenance too difficult
A good Poecilotheria regalis 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 Indian Ornamentals. Use long tools when useful and have a catch cup ready for rehousing.
Changing too much at once
Once an Indian Ornamental has settled, avoid repeatedly rearranging the enclosure for appearance. Stable housing usually matters more to Poecilotheria regalis than a constantly changing display.
If something needs correcting, change one clear husbandry problem at a time. That makes it easier to see whether Poecilotheria regalis settles, feeds and uses the enclosure normally afterward.