Suggestions for base rock?

[pulik]

Decided to quit mucking around, and go BIG! I'll be converting my 180 reef ready tank into a reef tank! I can't fill the tank with live rock though, so looking at options for base rock. Thought Lava rock would do nicely, except it's not available in white. Someone suggested Tufa; is that a good option? Any other suggestions? Would it be safe to buy from a landscape type place? Anything I need to know or be aware of?????

Thanks in advance for suggestions!