dmill15 and TimO If I haven't already said it then, welcome to the board!
dmill15 - Your use of tufa rock is not bad, it will hold coralline algea, it tends to be a soft rock. However it can also leach some metals into the water, depending on quality. I would think that 40 pounds of it is a good start for your baserock then add more if you like for your 50 gal, then seed it with however many pounds of live rock that you can get.
Most of us like to use calcium carbonate based rock such as figi is made from, whether we start out with dry base rock or liverock the calcium carbonate rock is the rock of first choice and in its dry form should cost no more than a dollar or two a pound.
TimO - Liverock can mean different things to different people;
You can have uncured liverock, cured livrock, fully cured liverock, baserock that turns into liverock (debateable timeframe here from months to 18 months).
Unseeded live rock - this could be the baserock that has been through a cycle of 2 months, this rock would have nothing except the benificial bacteria, and some algea.
Seeded live rock - to me this means that you have uncured or unseeded rock that is being seeded by fully cured ready to rock and roll liverock with all the benificial stuff we hope will some day be growing on our rocks.
Growing coralline aglea will take more than two months, growing sponges on you rock will take a while as well.
Hope that helps or HTH
Thomas
