Question about sand/ crushed coral

Hi, just thought of another question. In my 55 G. tank, I placed 30 lbs. of
crushed coral substrate. I now would like to add live sand to this. Is
there any problem with placing 30 lbs.(possible more for a DSB) of live sand
directly ontop of the crushed coral? I'd like to find an answer to this
question before I purchase my live rock and sand. By the way, I 'm thinking
of ordering my live rock and sand from e Tropics.com
http://www.etropicals.com/default.cfm?siteid=40 Any opinions about this
company? Thanks folks. Appreciate any help.

Oh, just thought of adding some more info. for any of you that might like to
give some pointers. Here is the equipment I have ready to set up:

55 G. glass aquarium
200 W. submersible heater
Aqua C Remora skimmer with Maxijet 1200 powerhead
Maxijet 400 powerhead (water movement)
another powerhead (don't have the specs. on this right now)
Coralife Aqualight CF 260 watts - 2x Actinic and 2x 10,000K lights
(the above mentioned) 30 lbs of crushed coral
Test kit from Red Sea (tests pH, alkilinity, nitrates, ammonia, nitrites,
and I think phosphates (not sure about the last one though, the kit is at
school right now so I can't be sure).

I am planning on setting up a reef tank for my seventh graders. But before
adding corals and then a few fish, I would like to cycle my tank with
liverock and sand, and let this run for a month or so before adding anything
else. Does this sound like a good idea? Any questions or comments would be
appreciated. Thanks.


Brian McCarty