Tetra's revolutionary aquarium gel foods come in two formats: Moist Gel Mix Pouches – nutritionally balanced blends of natural foods kept fresh in single serve pouches, and Gel Mix Grazing Blocks - block is dropped out of tray and sinks to the bottom of the aquarium where fish can eat at their own pace.the foods have a number of inherent advantages over dry foods and frozen foods. Tetranature gels feed more like how fish eat in nature and moist foods are highly attractive – ideal for finicky or shy fish. The sophisticated packaging process insures that foods are contaminant free, and no refrigeration is required.