Slate Rocks from HD

[Tightdog1]

go to any garden supply store. of look in your local creek or river to find good rocks. just be sure to wash/boil them before you put them in.

 

[congealedmeat]

lol, $2/lb is cheap. River rock from the pet store here costs $6/lb (Canadian, so ~$5 US)

On that note, I will never again pay for a rock for my tank, I just go down to the river and look for them myself. Just don't get stuff that is crystally or rusted looking. I know geodes are bad for aquariums, so I don't take chances with crystal.