We added about a little over 1/2 of a 25lb bucket of blue glass instead of the rocks it came with. Note: They fall Into the igniter, because of the small size, they need to be cleared or it won’t ignite properly. Ignitor switch on the backside is kinda cheap and does stick, but once mastered, it very nice addition to the back yard. Was very worth it! It will be beautiful this summer with this new addition.