Lava rock sources?
I'm building a filter and I want to use lava rock as the medium. I can't find any local sources (i'm in Eastern PA). Home Depot, Lowe's, Ace, Walmart - none of them have lava rock in their outdoor departments. i could order it online, but I'd really like to see what the volume of the package is. Simply knowing the weight of the bag/box doesn't help since the rock density varies. Any other places that might have it in the store?
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