Kathy Mormino (the-chicken-chick.com) wrote a lengthy article on why washed, coarse sand is the best poultry litter. You can find it here.

📍 Highlights of Sand as Litter

• Sand does not rot or decay—unlike other beddings which are a breeding ground for disease
• Sand has less dust and does not get as impacted or cakey
• Coarse sand drains better, which keeps quail feet healthy and disease free
• Sand evaporates ammonia at higher rates then normal litters or bedding
• Sand is eco-friendly, and is natural grit—which quail need
• Sand keeps cool in summer and warm in winter
• Quail have access to dust bathing and scratching 24/7 and year-round which are considered self-care behaviors

🌧 Warnings

If you live in an excessively wet and shady area, sand won’t be your best bet unless you can keep it dry. Make sure you use a quail home design that is on stilts, and use large overhangs to run off water. Have a plan during windy storms, such as having a tarp handy that you can quickly throw over and attach to the hutch.