Base rock?

[Fish]

You need to check out Ornamental ____ Supply off of 64 avenue N. (Sorry I forgot the name, starts with "ornamental" though).
They have huge containers full of tufa rock so you can pick out different shapes. It sells for around $0.40/lb !!!; infact, they didn't think that the 10lb rock I chose was even worth their time to ring through so they just gave it to me for free (personal results may vary )
Anyways, it has been working good for me so far. Besides, their tufa has, visually, just as much aquatic life on it as the "live rock" sold in our LFSs . I'm hoping that the beneficial bacteria will move over from my live rock and seed this stuff. Hope this helps.

- Chad