yeah i have red tufa in my 90 gallon and cant wait to get that out! lol.. if i were you, id go to your phonebook and look for local rock and landscaping yards.. thats what i did. i got 200 lbs of round river rock (in greens, grays and pinks) for less than 20 bucks...
its too expensive online (shipping is more than the cost of the rock! lol) and your local hardware stores wont carry what you need..