hi, just wanted to post my .02 to the original poster's comment, i have no desire to get in between the posting war that is going on right now.
I ordered TBS rock about 2 weeks ago. Yes the rock was collected and dumped on a private water lease. However, the rock (at least the rock i have received) is in fact real fossilized coral rock. Going over each piece of rock i see an incredible amount of porosity and each piece when I received it was absoutley teeming with all types of life. This is my very first tank, but the cycling process could not have been easier. My tank completely cycled in 5 days with ammonia not going over 0.50 at any time, and I only made ONE 10% water change, die-off was very minimal due to the fact that it spends virtually zero time out of water including being completely submerged during transit.
Yes you will get some hitchikers, but no risk = no reward. There is no other way to describe it other than to say the amount of life on the rock is unbelievable, something that needs to be seen rather than described. Obviously you need to make your own choice, although TBS is not the cheapest around I do it again in a heartbeat.
As for your original question about whether TBS rock is compatible with non TBS sand, as long as the sand is actual live sand and not just "bag sand" I think it is probably doable.
My understanding on DSB was that the finer the sand grain the better, as it is easier for sand sifting animals to move a greater volume of sand. Greater sand turnover rate = greater water throughput. I can't find the article right now, but there is one regarding DSB and a comparison of sand particle sizes somewhere on here.
Hope this helps!