What are Grorox? http://www.hydroasis.com/faq/faq-3.shtml

http://www.hydroasis.com/faq/faq-3.shtml
Where can I buy earthworms within Manila, Philippines?...
Answers:    Hydrokorrels are Dutch-made premium Leca (Lightweight expanded clay aggregate). These are the top choice for both hydroponics and hydroculture applications by Dutch growers. Clean and Dust Free Strong pebble structure doesn't crush Also known as Grorox, grow rocks, hydroton, and leca.

Hope this help.
How to grow sugarcane ?
they are great!! for growing orchids!