Microbiology - Cell Cultures and Characteristics - Discussion

If hydrolysis of the agar is suspected, a silica gel is used as a replacement solidifying agent.

Silica gel is a granular, vitreous, porous form of silicon dioxide made synthetically from sodium silicate. Most applications of silica gel require it to be dried, in which case it is called silica xerogel. For practical purposes, silica gel is often interchangeable with silica xerogel. Silica xerogel is tough and hard; it is more solid than common household gels like gelatin or agar.

Silica gel is often described as "absorbing" moisture, because silica gel removes moisture by adsorption onto the surface of its numerous pores rather than by absorption into the bulk of the gel.

What do you use silica get for? It can act as a carrying material but not a media.