The Astra 23" and the Finley 30" Fire Pits run on propane fuel and include 6.5 pounds of lava rock. We have chosen a basic gray for simplicity, but if you prefer something a little more colorful, many options are available online. Ensure any material you choose is intended for use in propane-based fire pits; regular rocks from your yard are not suitable.
Whether you decide to go with the included lava rock or a different fire glass, it is important to follow the assembly and safety instructions as outlined in the owner's manual. Maximum rock depth above the burner holes should not exceed 1/4" to avoid unburned gas pooling in the fire bowl, and the burner of the fire bowl must be covered completely to prevent the flame from extinguishing.