The Hydro-Sponge is manufactured by ATI and distributed by a wide variety of resellers, including Jehmco. An advantage to getting them from Jehmco is bulk pricing.
Some use power heads with sponges, especially when densities are kept high. Others use airflow to drive the flow of water through the sponge. Most use sponges as a secondary filter, combined with wet/ dry, HOB, or other filtration.
The ATI Hydro-Sponges sit on a perched base. This can create a microhabitat for hiding discus and accumulating debris. Thus some prefer to mount their sponges from the sides of a tank. The ATI ones are not so designed.
Borrowed from Dan @ GulfCoast:
Dan shared a DIY project for making this type of sponge somewhere here at SD.