[Delphinus]

Just going to throw in some observations to further confuse things.

First, placing rock on the sand, say a DSB, can be a problem if you have any kind of burrowing animal (eg. jawfish). The risk of toppling the entire reef structure is there, plus of course the risk of losing the burrowing animal because something fell on top of him (or "her").

Second, don't forget about different densities. When the tank is filled with water the "weight" of the rock on the glass at any contact point is going to be less than what it would be if the rock was sitting in a tank without water. Add to this that varying densities of rock (ie. some is less dense than others) then you can build up a pretty nice sized reef without really having to lose sleep worrying about whether your bottom plane is going to fail.

FWIW I'm setting up a 75g tank right now and I'm putting rock on the bottom but supporting the taller pieces with smaller rock. About 2" or 3" of sand is planned, and I'm hoping for the best. My existing tank is a 50 with a plenum. I had (until recently, that is) [img]images/smiles/icon_sad.gif[/img] a yellow-headed jawfish -- and his constant archeological/architectural excavations finally caused my plenum to fail (not to mention toppling several taller structures). So pretty much everything I say in my "point #1" above I am speaking from experience. Point #2 I am only speaking theoretically from my generally oversimplified view of things.

...

And on another note ... Ok, these snowflakes are very festive and all, but they're giving me a headache. I'm going back to work now!

[ 07 December 2001: Message edited by: delphinus ]