Originally Posted by
koiman1950
The closer you are to volcanic lava fields, the cheaper the price would be. As suggested, select the lightest pieces of what's available. It's usually the lighter colored gray rather than the darker blackish-gray. I used some stuff I got from Birdman several years ago, that he already had broken down and in gunny sacks. The pieces ranged in size from 2"x4"x2" to some softball size. It doesn't really matter that much, just mix the sizes together. What's most important is the flow rate over the rock and how clean the delivered water is to the shower unit. I found that using three layers of green Matala mat in the top tray has eliminated a lot of particulates from getting to the rock trays.