Sponge rock #3 is a great ingredient for do it yourself orchid potting mixes for seedling and miniature orchids. It adds light weight bulk as well as
Neblina Orchids, Paradera Aruba
Large Sponge Rock perlite Orchids
Perlite vs Vermiculite: What's the Difference? - Epic Gardening
Sponge Rock Perlite - Orchid Supply Store
Large Sponge Rock (#4) – Ravenvision Orchid Supplies
Sponge Rock #