Liquidfins,
We apologize for any misunderstanding regarding the habits of these specimens. Gobies of the genus Stonogobiops will move sand/gravel around as they help pistol shrimp dig a burrow. All gobies of the genus Stonogobiops form a bond with specific pistol shrimp, however they are not actually considered "Sand Sifting Gobies".
There are three types of gobies offered on our Live Aquaria site. They are Sand Sifters, Shrimp Gobies, and Small Gobies. When we have Yashia in stock they reside in the Shrimp goby section of the site. We also currently have several pairs in the Aquaculture Coral and Marine Life Facility that we plan to offer in our Divers Den site soon.
Gobies of the genus Valenciennea, Signigobius, Amblygobius, Amblygobius, are all considered Sand Sifting Gobies as they will take in mouthfuls of sand to extract small crustaceans such as copepods while the sand exits their operculum/gill covering.
We hope this clarifies the information you were interested in.
Donna Z.
Supervisors
LiveAquaria
Drs. Foster & Smith