Lava Rock

[Ethos]

The woman in my LFS said it wouldn't alter pH or any aspect of water chemistry, just wanted to confirm.

No I havn't experiencd any problems with it. Mine al;ways looks clean and doesn't show up anything, which is really a plus I think, because since I have a semi-planted FW tank I get a lot of algae.

 

[Erised]

You might want to check a local DIY shop or garden center for them instead of your LFS. The lava rock tends to be a lot cheaper there than in a lfs.
It will need more cleaning because of all the rock crumble/dust on it, but the money you safe will be worth it.