i've read on here that lava rock you buy isnt REAL lava rock and some people use the stuff you buy in there tanks.
i'd think the red stuff would turn your water red myself.
If you want cheap rock to use for a base rock I would look at calcium rock. Its light weight and cheap and builds a nice foundation for your nicer fuji rock. My LFS carries it for $2.00lb or I have even seen it on the internet auction sites.
lava rock will leech metals into your water. go with lace rock if available at your LFS, or you can even make your own if you are industrious enough
cheers!
it leaches calcium carbonate over a long period of time.... but that doesnt really hurt anything
it keeps the ph pretty stable
i just rinsed it off.
here is what it looks like.. (yellowish rock) but it turns green and brown like LR with time.