Petco was selling wheat grass packaged as "pet grass" in little pint-sized containers. No dirt, just a tightly woven root ball. My guys love this stuff and it looks great. I don't know how long it will last in the tank, but I was able to pull the roots apart & make three nice sized plantings out of it. They climb all over it and nibble on the blades of grass. At the base of each blade is a wheat seed where the seedling grew, and a few of them seem to love munching on those too.