calcium carbonate rock...

[kgb]

ok some question and as you know by now most of my questions a pretty lame but here goes.
ok for live rock oyu all pay 8 or 9 $ a pound? if so just a tip if you didnt know but golds when they have rock is only 6.99 a pound cured.
also i thought it was better to have rock that is porous and less dense(dont know why less dense but i thought i heard it some were)
ok this last question is unrelated really but i thought i read some where there a organisms or creatures or what ever that actually make live rock (like construct and make reef) is this true and if it is wouldnt it be possible to put some into yuour tank and eventualy habve more rock. because that would be nice to see the ever changing rock formations